
Where:
c(m) is the cost of the holiday in m miles,
If m greater than 10 there is a discount of $1
So the cost will reduce by $1

Add the like terms

This is the answer of (a)
The cost of the holiday was $7.5, which means
c(m) = 7.5
Let us substitute it in the equation above and find the value of m

Subtract 1 from both sides

Divide both sides by 0.5 to find m

m = 13 which is greater than 10
Lupe travel more than 10 miles
This is the answer of (b)