Answer :

500,000 *(1 + x) = 600,000
we're going to solve for x
first divide both sides by 500,000
1 + x = 1.2
subtract 1 from both sides 
x = 0.2

turn that into a percent by multiplying it by 100

0.2*100 = 20%

the magazine sales increased by 20%
so from 500,000 to 600,000
so assuming 500,000 is 100%
500,000+100,000=600,000
what is 100,000/500,000 in percent
percent means parts out of 100 so
3/100=3% so
100,000/500,000=100/500=20/100=20%

the naswer is 20%