Question 152639
"A farmer sold 7 goats, 11 chickens, 5 sheeps and 3 cows for U$980"
__ 7g+11c+5s+3c=980


"One goat costs 3 times as much as one chicken" __ 1g=3c __ g/3=c


"half as much as one sheep" __ g=s/2 __ 2g=s


"a quarter of the cost of one cow" __ g=c/4 __ 4g=c


substituting __ 7g+11(g/3)+5(2g)+3(4g)=980 __ 32 2/3 g=980 __ dividing by 32 2/3 __ g=30