The measures of the angles of a triangle are shown in the figure below. Solve for x. (2x+12)°
42°

2x + 12 = 42
-12. = -12
2x = 30
Divide by 2 = divided by 2
X= 15
That how you solve it

x=18
Explanation: So we know that when you add all angles together of a triangle it has to equal 180° and we know that one of the angles is 90° another is 42° and the last one is (2x+12)° so our equation would be
180=90+42+(2x+12)
add all the numbers that we can and get
180=2x+144
now subtract 144 from both sides so we could have the 2x by itself
36=2x
now to find the x we need to get rid of the 2 so we divide by 2 on both sides and get
18=x

38+105= 143, 39+104=143, and you will find then adding the numbers on opposite sides, moving inwards yields the answer 138 every time. because of this, you’re going to multiply 138 times the number of pairs, which is 34. therefore, 34*138= 4692(i’m sorry if it’s the wrong numbers, but it’s the right concept)