6 subtracted from the product of 5 and a number is 68

6 subtracted from the product of 5 and a number is 68

Take this algebraic expression in parts.

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

The product of 5 and this number is:
5x

We subtract 6 from 5x:
5x - 6

The phrase is means an equation, so we set 5x - 6 equal to 68
5x - 6 = 68