Step-by-step explanation:
x = number hours dog walking
y = number hours tutoring
x + y <= 11
6x + 10y >= 80
the solution is the common area below the first line and above the second line.
the first line is above the second line (due to the y-intercept of 11 vs. 8) until the crossing point.
for the crossing point we use the regular equations :
from the first we get
x = 11 - y
using this in the second
6×(11 - y) + 10y = 80
66 - 6y + 10y = 80
4y = 14
y = 14/4 = 7/2 = 3.5
x = 11 - y = 11 - 3.5 = 7.5
so, she has to do at least 3.5 hours tutoring (and then 7.5 hours dog walking) for the minimum of $80 earning, all the way up to the maximum of 11 hours tutoring (and 0 dog walking) for $110 earning.
