Question 1133195
Basically, he did it fine, but I think the teacher may have wanted him to set up the variable and take $25 off it.
x=the original price
25 off the original price is x-25
That is equal to $150
so x-25=$150, and x+$150+$25, or $175.
I would at least give partial credit.

The purpose of this type of problem is to make students define the variable and set up the equation for more complex problems.

If the bicycle is on sale for $150, and it is 25% off the original price, what was the original price?  One can do that in one's head, perhaps, but it is much easier to make a mistake.
x=orignal price, so 0.75x-sale price.  The sale price is $200, so 0.75x=$150, x=$200.  That is a lot easier (faster and safer, too) than guessing and checking.

A lot of word problems can be dealt with in many ways.  If there is a problem about 25% off, that can mean 75% of the original OR, one can calculate the 25% off and subtract it from the original amount. Both of those ways are acceptable.

Sometimes, it is easier to do one way than the other.  Alex is 4 years less than twice as old as Bob.  Here, Bob is the youngest, so let his age be x, not Alex's age, where Bob will be some fractional amount of age.  If Bob is x then Alex is 2x-4, which is 4 fewer than twice as much.