Question

(a×7+a×8-a×15)1+2+3+.......+10

Answer 1

( a x 7 + a x 8 - a x 15 ) x 1 + 2 + 3 + ... + 10 

= a x ( 7 + 8 - 15 ) x 1 + 2 + 3 + ... + 10

= a x 0 x 1 + [ ( 10 + 2 ) x ( 10 - 2 ) x 1 + 1 ]  :  2 

= 0 + [ 12 x 9 ] : 2 

= 0 + 54

= 54 

Answer 2

\(\left(a\times7+a\times8-a\times15\right)\times1+2+3+...+10.\)

\(=a\times\left(7+8-15\right)\times1+2+3+...+10.\)

\(=a\times0\times1+\left[\left(10+2\right)\times\left(10-2\right)\times1+1\right]:2.\)

\(=0+\left(12\times9\right):2.\)

\(=0+108:2.\)

\(=0+54.\)

\(=54.\)