Question

7a+8b=22 si a+2b=4 afla a

Answer 1

7a+8b=22
a+2b=4 ⇒a=4-2b  deci
7a+8b=22=7(4-2b)+8b=2228-14b+8b=22
28-22=6b
6=6b
b=1  dar  a=4-2b⇒ a=4-(2×1)=2
⇒a=2
verificare
a+2b=4
2+2×1=4
2+2=4
4=4

deci a=2 si b=1

Answer 2

$7a+8b=22 \\ a+2b=4$(inmultim cu 4)
$4a+8b=16 \\ 7a-4a=22-16 \\ 3a=6 \\ a=\frac{6}{3} \\ a=2$