Remark
The easiest way to graph this is to get a program to do it for you. Desmos is ideal.
Problem 7a
The graph is down below the rest of the answer. 5x + 2y = 150
x and y intercepts.
The x intercept is marked as 30. That was derived by letting y = 0 to get
5x = 150 divide by 5
x = 150 / 5
x = 30
So if you buy NO wristbands, you can get 30 keychains
The y intercept occurs when x = 0
2y = 150 Divide by 2
y = 150 / 2
y = 75 That means if you buy NO keychains, you can buy 75 wrist bands.
Problem 7b
For this problem x = 18
5*18 + 2y = 150
90 + 2y = 150 Subtract 90 from both sides.
2y = 150 - 90
2y = 60 Divide by 2
y = 60/2
y = 30
Conclusion
You can buy 18 key chains (given)
You can buy 30 wristbands (calculated)