Question

calculati ecuatia 7a+3b=29 a+ b= 7

Answer 1

7a+3b=29
a+b=7
a=b-7
7 x b-7+3b=29
7b-49+3b=29
10b=49-29
10b=  20
b=2
a= 5

Answer 2

$\displaystyle 7a+3b=29 \\ a+b=7 \Rightarrow a=7-b \\ 7a+3b=29 \Rightarrow 7(7-b)+3b=29 \Rightarrow 49-7b+3b=29 \Rightarrow \\ ~~~~~~~~~~~~~~~~~~~~~\Rightarrow-7b+3b=29-49 \Rightarrow -4b=-20 \Rightarrow \\ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ \Rightarrow b= \frac{-20}{-4} \Rightarrow \boxed{b=5} \\ a=7-b \Rightarrow a=7-5 \Rightarrow \boxed{a=2}$