If 2/7 of a ton of concrete covers 7/8 of a wall, how many tons of concrete are required to cover the entire wall?

We can solve this as a proportion..

(2/7) ton  / (7/8) wall = x tons  / 1 wall    .....cross-multiply......

(2/7)  = (7/8)x     multiply both sides by 8/7 .... so we have..

(8/7)(2/7) = x  = 16/49 tons