280 is what percent of 400?

Can someone me out here and the tell me the greatest common factor

Serena is making an experiment. for that, she needs 20 grams of a 52% solution of salt. she has two large bottles of salt water: one with 40% and the other with 70% of salt in them. how much of each must she use to make the solution she needs? i am in need of

Maci and i are making a small kite. two sides are 10". two sides are 5". the shorter diagonal is 6". round all your answers to the nearest tenth. 1. what is the distance from the peak of the kite to the intersection of the diagonals? 2. what is the distance from intersection of the diagonals to the top of the tail? 3. what is the length of the longer diagonal?