Answer:
lisa would earn more money
Explanation:
let say mary base price = x
mary per student price = y
x+15y = 90
x+8y = 62
7y = 28
y =4
x = 30
mary will earn for 20 students = 30 + 20*4 = 110
lisa base money = 30/2= 15
lisa per student = 4*2=8
lisa earning for 20 students
= 15 + 20*8 = 175
lisa will earn more money