So first start out by writing an expression for the cost of the child and the adult separately.
Child:
6 + 1r ($6 + $1 per ride)
Adult:
10 + 1.5r ($10 + $1.50 per ride)
to find how much more the adult will spend, just do Adult Expression - Child Expression which will be:
10 + 1.5r - (6 + 1r) just simplify this
For Part B, use your equation from part A where r = 7
Answer: B (-12, 15)
Step: (3×-4) =-12
And (3×5)= 15
87 24/25.......24/25 = 0.96......answer is 87.96
224 7/10....7/10 = 0.7....answer is 224.7
686 49/50...49/50 = 0.98...answer is 686.98