a) 35.34 + 35.86 + 65.75 + 65.45 =
( 35 + 65 ) x ( 34 + 86 ) + ( 75 + 45 )
100 x 120 x 120
100 x 14400
1440000
\(35\cdot34+35\cdot86+65\cdot75+65\cdot45\\ =35\cdot\left(34+86\right)+65\cdot\left(75+45\right)\\ =35\cdot120+65\cdot120\\ =120\cdot\left(35+65\right)\\ =120\cdot100\\ =12000\)