25 * 5 + 15 * 3 - 40 * 2 =
125 + 45 - 80 =
170 - 80 =
90
A^2-5a = 6
a^2-5a-6 = 0
Discriminant = (-5)^2-4(1)(-6) = 49
Discriminant is positive so there are two solutions
We have 35 - 5 = 30 levels left to beat.
The question is asking us for the levels left to beat, to the ones that already have been beaten:
30 : 5
Simplified;
6 : 1
Zero
There is no solution for these equations as there is no even one point of intersection between them