## Answer :

10% -----------80

100% ---------x

Crossmultiply now

10*x=100*80

10x=8000 /:10

x=800 - its the answer

33.333% -----------21

100% --------------x

crossmultiply

33.33x=21*100

33.33x=2100 /:33.33

x=63 - its the answeer

2. 33.333% of what number is 21?

10% -----------80

100% ---------x

Crossmultiply now

10*x=100*80

10x=8000 /:10

x=800 - its the answer

33.333% -----------21

100% --------------x

crossmultiply

33.33x=21*100

33.33x=2100 /:33.33

x=63 - its the answeer