how do i solve these quadratics? c=10000

Question

9a+3b+c=7975
36a+6b+c=6400

im unsure of how to solve as a and b are unknowns...

Answer 1

Step #1 is to replace c with 10000 in both equations to get

9a + 3b = -2025 ---> 3a + b = -675

36a + 6b = -3600 --> 6a + b = -600
subtract the two equations:
3a = 75
a = 25

plug that into 3a + b = -675
75 + b = -675
b = -750

check:
9(25) + 3(-750) + 10000 = 7975 check!
36(25) + 6(-750) + 10000=6400, check!

my answers are correct

Answer 2

btw, these were not quadratics

I find it strange that a person taking Calculus would not know how to solve two linear equations with two unknowns.