Question

The total value of exports rose significantly between 1970 and 1980 find the percent increase in exports during this period

Answer 1

This is not a full question.  If you were given the amount at the begining of 1970 (we'll call it x) and the amount at the end of 1980 (we'll call it y), we should solve them accordingly:
y-x=? (calling the answer a)
a/y=%(not answer yet, call this b)
b+100=answer