The student didn't make any mistake. The slope of the line between those points is 3/8.
Financial aid would cover 5,700 and you would need to pay 1,900
work shown above! basically each coordinate is opposite so the new coordinates would be A(0,-3) B(-2,4) C(4,6)
Substitute
12(3) + (52)
12(3) = 36
36 + 52 = 88