Use the guess-and-check method to solve the equation: 40x = 30(x + 2)

Don't know why they'd encourage a "guess-and-check" method.

But let's play their game.

Choose x=2 (I just invented it):    Is 40(2) = 30(2+2)?  Is 80 = 120?  No.

Try x=1, x=3, etc.

Better yet, do the problem algebraically:  40x = 30x + 60, or 10x = 60.
Then x=6.      Check:  Is 40(6) = 30(6+2)?  Is 240 = 30(8)?  YES.

  x=6

Bis the right answer