Answer:
addition and subtraction is possible when denominator are same so to make denometor same multiplication is use on both numerator and denominator
Explanation:
for example,
5/10+2/5
now we can't add those numbers so
multiply on both on numerator denominator by same number to make denominator same.
look
5*1/10*1 + 2*2/5*2
5/10+4/10.
(addition is possible bcz denominator are same)
(5+4)/10
9/10 is answer