A = 3/5 + 6/5 ? A= 3/5+6/5=9/5
B = 5/12 + 4/3 ? B=5/12+[(4*4)/(3*4)]=5/12+16/12=21/12
C = 5/18 + 1/12 ? C=[(5*12)/(18*12)]+(1*18)/(12*18)=(60/216)+(18/216)=78/216
D = 3/5 - 6/5 ? D=3/5-6/5=-3/5
E = 7/4 - ( - 3/12) ? E=[(7*3)/(4*3)]+3/12=21/12+3/12=24/12=2
F = - 4/3 - 3/5 ? F=[(-4*5)/(3*5)]-[(3*3)/(5*3)=-20/15-9/15=-29/15
