twice the difference of a number and 55 is equal to 3 times the sum of a number and 8

twice the difference of a number and 55 is equal to 3 times the sum of a number and 8

Take this algebraic expression in pieces.

Left side: The phrase a number means an arbitrary variable, let's call it x.
x

The difference of this number and 55 means we subtract 55 from x
x - 55

Twice the difference means we multiply x - 55 by 2
2(x - 55)

Right side: The phrase a number means an arbitrary variable, let's call it x.
x

The sum of a number and 8 means we add 8 to x
x + 8

3 times the sum means we multiply x + 8 by 3
3(x + 8)

Now that we have the left and right side of the expressions, we see the phrase is equal to. This means an equation, so we set the left side equal to the right side:
2(x - 55) = 3(x + 8)