5/12а+7 при а =4 4/9 б+2/3 при б=3/4 2/5+1 целая 1/45 при а=1 целая 3/5
5/12*4+7=20/3+7/1=41/3 4/9*3/4+2/3=1/3+2/3=1 2/5*1 3/5+1 1/45=2/5*18/5=36/25+1 1/45=1 329/225