[Music] welcome to math with Mr J in this video I'm going to cover how to find the missing angle measure of a triangle now remember the sum of the angles for every triangle is 180° that just means that when we add the three angles of any triangle they will always equal 180° we need to know this information in order to find a missing angle measure of a triangle let's jump into our examples starting with number one where we have a triangle with a 98° angle a 31° angle and then X represents the missing angle measure so how do we go about this well we know that these three angles need to add up to 180° so let's set up an equation in order to solve 4X so we have 98° + 31° + x equals 180° now let's figure out what x equals so we need to solve 4X let's start by adding the two angles that we are given so 98° plus 31° that gives us 129° + x = 180° now we need to isolate X we need to figure out what x equals we do this by subtracting 129 from the left side of the equation whatever we do to one side of the equation we must do to the other in order to keep it balanced so let's subtract 129 from the right side as as well the 129s on the left side of the equation cancel each other out so X is now isolated x equals and then on the right side of the equation 180 -29 gives us 51 and this is degrees so x equals 51° so that means that this missing angle measure is 51° now we set everything up as an equation and worked through that equation in order to solve for x but essentially all we did was add the two angle measures that we were given and then we subtracted that from 180° in order to find the missing angle measure let's move on to number two where we have a triangle with a 90° angle a 24° angle and then X represents the missing angle measure let's set this up as an equation and work through it in order to figure out what x equals so we have 90° plus 24° + x equal 180° let's start by adding the two angles that we were given so 90° + 24° that gives us 114° + x = 180° now we need to isolate X we need to figure out what x equals so let's subtract 114 from the left side of the equation whatever we do to one side of the equation we must do to the other so subtract 114 from the right side as well the 114s on the left side of the equation cancel each other out so X is now isolated x equals and then on the right side of the equation 180- 114 gives us 66 and this is deges so x equal 66° 66° is our missing angle measure now again we set that up as an equation and solved for X so we worked through that equation in order to figure out what x equaled but basically all we did was add the two angle measures that we were given and then we subtracted that from 180° in order to figure out the missing angle measure so there you have it there's how to find the missing or unknown angle of a triangle I hope that helped thanks so much for watching until next time peace