Let me take a stab at this...these are quite confusing and difficult! I made a table like this:
mL sol. % amt%
29% x .29 = .29x
51% 44 .51 = 22.44
--------------------------------------------------------
37% 44+x .37 = .37(44+x)
You have to add the first two rows together to give you what you want in the end. In other words, how much (x) of a 29% solution (.29) + 44mL of 51% (.51) solution will give you a solution of 37% (.37). The word "of" in those phrases mean to multiply: .29x + 22.44 = .37(44+x). Distribute the .37 into the parenthesis to get .29x + 22.44 = 16.28 + .37x. Solve for x to get x=77 mL
