40 = -3.5x + 7 + 6.5x

x = 11

Step-by-step explanation:

I just took a test that had this question. I hope this helps

answer: yes, he is correct

step-by-step explanation: 10x-1=59

                                              1-1=0     59+1=60

60/10=x=6

second option

step-by-step explanation:

the measures of a triangle equal 180. use that to find x.

2x+3x+4x=180

9x=180

9x/9=180/9

x=20

now you know x, you know angle a is 40°, angle b is 60°, angle c is 80°.

because angle a is 40°, the first option doesn't work.

because angle b is 60°, the second option does work.

when you add angle a and b, you get 100°. complementary means it equals 90°, so the third option doesn't work.

when you add angle a and c, you get 120°, which is not 100.