Question

helpp pleasee

solve by substitution

3a+b+c=7
a+3b-c=13
b=2a-1

Answer 1

can someone help explain it please

Answer 2

it will take a sec

Answer 3

we are going to give each equations names to simplify the process.
1. 3a + b + c = 7
2. a+3b-c=13
3. b=2a-1

then plug equation 3 into equation 1 to get,
3a + 2a - 1 + c = 7
5a - 1 + c = 7
c = 8-5a, make this equation 4.

then plug equation 4 and 3 into equation 2 to get:
a + 3(2a-1) - (8-5a) = 13
a + 6a -3 -8 +5a = 13
12a - 11 = 13
12 a = 24
a = 2.

Now go back to equation 4 and plug a in to get:
c = 8 - 5(2)
c = -2

then plug a into equation 3:
b = 2(2) -1
b = 4 -1
b = 3

so the answer is a = 2, b=3, c =-2