Wow! Here you have 3 fractions with 3 different denominators that have nothing in common. In cases such as this one you find the LCD by mult. all of the given denominators together. Thus, in this case, your LCD is 4(5)(3) = 60.
To find the least common denominator of the three fractions, list out the multiples of each denominator:
Multiples of 3: {3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60} Multiples of 4: {4,8,12,16,20,24,28,32,36,40,44,50,55,60} Multiples of 5: {5,10,15,20,25,30,35,40,45,50,55,60}
The least common denominator of these three fractions is 60.
It will be c- 20: 4q and 2(q+30) have to equal the same therefore q=30 which makes both these equations equal. 3p + 4q then have to equal 180 as they are on a straight line so you know q=30 so 4x30=120 so 180-120=60 Then 60/3=20 and that is your answer. Hope this helps :)
