math
posted by lily .
a framer divides his herd of cows anong his 4 sons, one get 1/2, second get 1/4, 3rd gets 1/5 and the 4th get 7. how many cows are in the herd?

x/2 + x/4 + x/5 + 7 = x
multiply each term by 20 and solve, it's easy from there. 
thank you for your help.i got 26 as the answer. i am not sure if this is correct. i am only in the 7th grade and this is the first time i am doing this kind of problem. could you please explain a little more.

ok, let's do it without algebra
so far he has given away 1/2, 1/4 and 1/5 of the herd
1/2 + 1/4 + 1/5
= 10/20 + 5/20 + 4/20
= 19/20 of the herd, leaving 1/20
but it said the 4th son get 7 cows, so he must have received 1/20
then if 1/20 equals 7 then
20/20 , or the whole herd, must have been 20x7 or 140 cows
check:
1/2 of 140 = 70
1/4 of 140 = 35
1/5 of 140 = 28
sum of 70+35+28+7 = 140 
oooooooooooooooo that makes alot more sense, thank you!