Question

3. Solve the system of equations using linear combination.

a + c = 9
8a + 4.5c = 58

Answer 1

Hey I have posted a picture the method I use to solve simultaneous equations is change the sign and follow the new sign.
This involves changing the sign for the second equation and solving it

Answer 2

a+c=9 so a=9-c
8(9-c)=72-8c+4.5c=58
12.5c=58-72
12.5c=-14
c=-1.12