In order to prove that Barb has enough money, we know that the sum of the three purchases must be less than or equal to 35. This can be expressed as an inequality:
a + b + c ≤ 35
Insert any known values:
11.25 + 15.50 + 10.75 ≤ 35
Simplify the left side of the inequality:
37.5 ≤ 35
This inequality is not true: 37.5 is not less than or equal to 35. Therefore, Barb does not have enough money to cover her purchases.
I hope this helps!