What you do is you rearrange and simplify both equations to have them in terms of y, and then graph them. If it asked for a solution, their point of intersection would be the solution.
Answer:
The slope is 5x and the y-intercept is -7
Step-by-step explanation:
2( coin faces) 8( number of times)
Sally earns per hour = $12
Sally works for in a week = 16 hours.
So, Sally earns in a week = 
Sally can save money each week= 20% of 192

A. How much does she earn each week ? Sally earns $192 in a week.
B. How much money will she save each week? Sally will save $38.40 each week.
C. How much money will she save each month (assume there are 4.3 weeks in a month)
Savings of 1 week = $ 38.40
Savings of 4.3 weeks = 
Hence, she will save $165.12 in a month.
D. How many months will it take her to save the money?
Total money needed = $1800
Number of months needed to collect this amount =

Hence, it will take 11 months approx to save $1800.
Slope is 2 and the y intercept is 4