Emma:
Number of hours = 4
Total cost = 18
Where x is the cost per hour n and y is the flat fee
18 = 4x + y
Louise:
number of hours = 7
total cost = 25.50
25.50 = 7x + y
We have the system of equation:
18 = 4x + y
25.50 = 7x + y
Solve the first equation for y
18-4x = y
y = 18-4x
Replace y on the second equation; and solve for x
25.50 = 7x + (18-4x)
25.50 = 7x + 18 -4x
25.50 = 3x + 18
25.50 - 18 = 3x
7.5 = 3x
7.5/3 = x
2.5 = x
a. Cost per hour = $2.5
Now, replace x on any equation and solve for y
18 = 4x + y
18 = 4 (2.5) + y
18 = 10 +y
18 - 10 = y
8 = y
b. Flat fee = $8
c. Use the equation:
Cost = flat fee + cost per hourx (number of hour)
Cost = 8 + 2.5 (2)
Cost = 8 + 5 = $13