Question

42 is 30% of what number

Answer 1

30%
percent means parts out of 100 so 30%=30/100=3/10

42 is 3/10 of x
'of' can be translated to multiply
42=3/10 times x
multiply both sides by 10/3 to get rid of fraction
420/3=x
140=x

the number is 140

Answer 2

140.
Take 42/30% and you get 140
Hope this helps!