Greg had $17 more than Fred, and together they had just enough money to by their mom a present that costs $85. How much money did Greg have?

Greg had $51 while Fred had $34.

Greg has $17 more than Fred: 51-34 = 17

Together, their money is enough to get their mom a present that costs $85 ($51 + $34 = $85)

So Greg have $51.

Define x:

Let Fred had x dollar.

Fred = x

Greg = x + 17

Solve x:

x + x + 17 = 85

2x + 17 = 85

2x = 68

x = 34

Find the amount each of them had:

Fred = x = $34

Greg = x + 17 = 34 + 17 = $51

Answer: Greg had $51