to add them, we need to make the bottom nmbers the same
the bottom number are 7 and 9
remmeber taht x times 1=x it doesn't change
also that x/x=1 such taht x=x
so
change the bottom number of the fraction without chanign the value of the fraction by multipliying it by 1
16/7 times 9/9=144/63
17/9 times 7/7=119/63
now we have
144/63-119/63=
(144-119)/63=
25/63
