Asked by Angie

Using the substitution method, what is the value of a in the solution to the system of equations below?
a=3b+7
4a+9b=70
Answered by Ms. Sue
4a+9b=70

4(3b + 7) + 9b = 70

12b + 28 + 9b = 70

21b = 70 - 28

21b = 42

b = 2

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a=3b+7

a = (3 * 2) + 7

a = 13


Answered by Riana
a=3b+7...eq (1)
4a+9b=70 or 4a=-9b+70...eq (2)
multiplying equation i by 3
3(a)=3(3b+7)...eq (1)
3a=9b+21...eq (3)

subtracting equation (2) from eq(3)
4a=-9b+70...eq(2)
3a=9b+21...eq (3)

a = 49
this is the value of a
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