\(a\left(2+13\right)+\left(3+12\right)+\left(4+11\right)+\left(5+10\right)+\left(6+9\right)+\left(7+8\right)=15+15+15+15+15+15=90\)
\(b8\left(3+2+4\right)=\)8x9=72
a) 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 + 11 + 12 + 13
= (2 + 13) + (3 + 12) + (4 + 11) + (5 + 10) + (6 + 9) + (7 + 8)
= 15 + 15 + 15 + 15 + 15 + 15
= 90
b) 8 x 3 + 2 x 8 + 4 x 8
= 8 x (3 + 2 + 4)
= 8 x 9
= 72
a(2+13)+(3+12)+(4+11)+(5+10)+(6+9)+(7+8)=15+15+15+15+15+15=90a(2+13)+(3+12)+(4+11)+(5+10)+(6+9)+(7+8)=15+15+15+15+15+15=90
b8(3+2+4)=b8(3+2+4)=8x9=72
