There are twenty-one benches of two kinds in the room. One has three legs each and the other has four legs each. There are eighty legs in all. How many benches are there with three legs and how many with four leg?
A.3 three-leg and 18 four-leg.
B.4 three-leg and 17 four-leg.
C.5 three-leg and 16 four-leg.
D.2 three-leg and 19 four-leg.
网友回答
B