in this video we're going to cover how to do questions like these where you have to rearrange formulas to get a particular letter by itself to do these questions you do basically the same thing as when you solve equations so you just rearrange the formula until you get the letter that you've been asked to find all by itself in this first question on the left they're asking us to make x the subject so we need to end up with just an x on the left hand side equals something on the right to do this we first of all want to get the x by itself by getting rid of this 4 and this 3. so to get rid of the 4 we take our equation and just subtract 4 from both sides giving us y minus 4 equals 3x and to get rid of the 3 we just divide both sides by 3 but importantly it's the whole of the y minus 4 that we're dividing by 3 and that will equal a single x the more common way to write this though is to show the division using a fraction line with a 3 on the bottom which still means divided by 3 but this way you don't need to bother with the brackets and again we'll still have x on the right then the very last thing we need to do is swap the two sides around to write it as x equals y minus four over three so that our x is on the left and counts as a subject of the equation for this second question you need to get the b by itself so first you need to get rid of the minus 5 by adding 5 to both sides so that you get a plus five equals b over three next you need to get rid of the divided by three fraction by multiplying both sides by three but just like in the last question this means that you have to multiply everything on the left hand side by three so you can put the a plus five in a bracket and multiply the whole thing by three which you can then expand to three a plus fifteen equals b and lastly we just swap it around to get b equals 3a plus 15. let's try a couple more for this first one the x that we're trying to get by itself is inside a bracket so the first thing we need to do is expand the bracket by multiplying the 3 by the 2 and the x giving us 2y equals 6 plus 3x next we need to get rid of the 6 by subtracting 6 from both sides to get 2y minus 6 equals 3x and then we can divide both sides by three so you get two y minus six all over three equals x which we can then swap around to get x equals two y minus six all over three as our final answer for the last question the first thing we do is subtract three from both sides to get six a minus three equals b over two then to get b by itself you just multiply both sides by two and again it'll be the whole six a minus three that you need to multiply by the two so you can expand the bracket by multiplying the two by six a to get 12a and by minus 3 to get minus 6 which will all equal b so our final answer will be b equals 12a minus 6. anyways that's everything for this video so if you found it useful then please do give us a like and subscribe and thanks for watching you