Answer:
67.5
Explanation:
his earnings increase in a linear way so we can express it as linear equation;
y = ax+ b ,
a is the slope in this case it is 7.5$ for every hour
b is the initial value, in this case 0
y = 7.5x
we will write 9 insted of x to find the amount of money when working for 9 hours;
y = 7.5 x 9 = 67.5