Answer:
70 rupees
Explanation:
First set up an equation to find out what the "sum of money" is. We know that 12% of it is 42, so the equation looks like this:
0.12x = 42
Remember that with percents you always convert them into a decimal by dividing by 100. (Per century, or per one hundred, something like that.)
Next, solve for x by dividing both sides by 0.12:
x = 42/0.12 = 350
Now that we know what the "sum of money" is, we can take 20% of it:
0.20(350) = 70 rupees