\(123\times35+124\times65\)
\(=123\times35+\left(123+1\right)\times65\)
\(=123\times35+123\times65+65\)
\(=123\times\left(35+65\right)+65\)
\(=123\times100+65\)
\(=12300+65\)
\(=12365\)
123 x 35 + 124 x 65
= 123 x 35 + 123 x 65 + 65
= 123 x (35 + 65) + 65
= 123 x 100 + 65
= 12300 + 65
= 12365