Question

stiind ca a+c=10 si a+b=8 calculati 15a+5b+10c

Answer 1

a+c=10 10a+10c=10×10=100
a+b=8 5a+5b=8×5=40
15a+5b+10c=100+40
=140

Answer 2

a + c = 10   si   a + b = 8

15 a + 5 b + 10 c = 140

= 10 a + 10 c + 5 a + 5 b =

= 10 × ( a + c ) + 5 × ( a + b ) =

= 10 × 10 + 5 × 8 =

= 100 + 40 =

= 140