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)
You want to multiply 87.60 and 25.60 by 10. 87.60x10=876. 25.60x10=256.876-256=620. Then you will take 1/4 of 620 to get the answer 155 is what she paid for lessons.