There are 5 options. Let's figure out which ones are wrong, and why:
y + y + y = y(1 + 1 + 1)
This one is correct, because of the distributive property. Another equivalent is 3y.
2a + 2b = 4ab
This one is incorrect, as you are not multiplying the numbers.
3 · (2 + x) = 6 + 3x
This one is correct, because of the distributive property
2t + 3t = 5t
This is correct, as you can add variables together as long as all the variables are the same
x + 3 = 4x
This is not correct, as 4x is 4 x's.
