For (a) the simplest fraction for 6/42 is 1/7 - You get this by 42 divided by 6=7 and 6 divided by 6=1
(b) 6/42 turned into a decimal is 0.14 - to turn into decimal divide 6 by 42=0.14285714
(c) 0.1 converted to a percentage is 10%- you get this by multiplying the decimal by 100.