Question 769652
.50*700=350 tin
.25*700=175 lead
(a + 350 ) / ( a + b + 700 ) = .60,
( b + 175 ) / ( a + b + 700 ) = .20 
a=175., add 175 tin
b=0. add 0 lead

525/875=.6

175/875=.2