Question 112140
When your instructor asked for an equation he meant for you to include variables.    

You gave a true mathematical statement, but an equation involves unknown numbers.

In order to change your statement into an equation, you could substitte the 22 for an x.

Instead of 8 + 5(22) = 118
you could have 8 + 5(x) =118

In equations, we have to be able to solve for an unknown.  In substituting 22 for x, we're allowing someone to solve for the value of the variable.
That's the difference between staements and equations.