Question

9a+4b+5c stiind ca a+b=10/3 si a+c=5

Answer 1

a+b=10/3 I *4
a+c=5 I *5

4a+4b=40/3
5a+5c=25(+)

4a+5a+4b+5c=40/3+25
9a+4b+5c=40/3+75/3
9a+4b+5c=115/3

Answer 2

9a+4b+5c = ? a+b = 10÷3 |×3 => 3a+3b = 10 a+c = 5 |×5 => 5a+5c = 25 (3a+5a)+5c+3b = 8a+5c+3b =25+10=35 => mai avem nevoie de a+b => a+b = 10÷3 35+10÷3 = 38