I have a friend Robert who is an expert at taking the difference of consecutive perfect squares. This means that if I give him a number $x$, he immediately computes $$x^2 - (x - 1)^2$$and gives me the result. I decided one day to first give Robert the number $9$, then the number $6$, and finally the number $4$. Robert gave me three numbers in return. What is the sum of these three numbers?

35

Step-by-step explanation:

Please look at the attachment down below.

Hope this helped! :)

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.