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If 7a+3b=20 and 3a+7b=10, what is a+b?

Sagot :

Answer:

3

Step-by-step explanation:

7a+3b=20

3a+7b=10

Substitution:

[tex]\begin{bmatrix}3\cdot \frac{20-3b}{7}+7b=10\end{bmatrix}[/tex]

[tex]a=\frac{20-3\cdot \frac{1}{4}}{7}[/tex]

[tex]a=\frac{11}{4},\:b=\frac{1}{4}[/tex]

11=4 + 1=4 = 12/4

12/4 = 3