Answer: 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