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?

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

Oh the third equation was

a+3b+10c=131

To solve the linear equation 2a + 3 + c = 28, you will need to isolate the variable "a". Here's how you can proceed:

1. First, simplify the equation by combining like terms: 2a + c + 3 = 28.

2. Next, move the constant term (3) to the other side of the equation. You can do this by subtracting 3 from both sides: 2a + c = 28 - 3.

3. Simplify further: 2a + c = 25.

Now, the equation 2a + c = 25 represents a system of equations with one equation and two variables. To solve for "a" in terms of "c", there needs to be another equation that relates "a" and "c".

Are there any other equations or constraints provided in the problem that could help solve for "a" and "c"?