Ok, so we know 42 is 70%, 7/10. We need to get from 70% to 100%. To do so, we must divide 70% by 7 to get 10%. 42 divided by 7= 6. 6 = 10% (or one tenth). We now need to multiply by 10 to get 100%. 6 x 10= 60. 60=100%.
Therefore we know that 42 is 70% of 60.