Write these fractions in least common denominator2/5x+15y 1/2x+6y

Look at deonomators

assuming that the deonomenators are 5x+15y and 2x+6y

find their LCM

factor

5x+15y=5 (x+3y)

2x+6y=2 (x+3y)

LCM=10 (x+3y) = 10x+30y

multiply 2 / (5x+15y) by 2/2=4 / (10x+30y)

multiply 1 / (2x+6y) by 5/5=5 / (10x+30y)

if we add them

9 / (10x+30y)