Question

a+b+c=28
b= a+3
I plugged in the b but got stuck on 2a+3+c.
What I did:
a+a+3+c=28
2a+3+c=28, but what do I do next to solver this linear equation?

Answer 1

since you have 3 unknowns you will need 3 distinct equations.
I see only two.

so all you can do is say:
2a + c = 25

Answer 2

Oh the third equation was
a+3b+10c=131