Question

If a + 3b = 13 and a + b = 5, the value of b is?

A. 1
B. 4.5
C. 7
D. 4

Answer 1

Ans: D
First, multiply a+b=5 by 3 to make it 3a+3b=15
Second, subtract this equation from a+3b=13 to give 2a=2
Therefore, a=1
Substitute this into a+3b=13, to give 1+3b=13
So, 3b=12
Divide this 3b=12 by 3 to get for.
Therefore, b=4

Answer 2

the value of b is 4

a=1

1+3(4)=13
1+4=5