Question

5a-8c при a=0,2 c=2/14              /-дробь

Answer 1

5а-8с=5*0.2-8*2/14=1-8/7=-1/7

Answer 2

5a-8c 
 a=0,2   $c= \frac{2}{14} = \frac{1}{7}$ 
$5*0,2-8* \frac{1}{7} =1- \frac{8}{7} = \frac{7-8}{7} =- \frac{1}{7}$