6/（35*（2/5+2/7））*4.8
=6/（2*7 + 2*5）*4.8
=6/24*4.8
=6*4.8/24
=6*0.2
=1.2
4/19 *16/13-6/19*2/13
= 64/(19*13)-12/(19*13)
=(64-12)/(19*13)
=52/(19*13)
=13*4/(19*13)
=4/19