Question 1135642
x grams of 40% and 20-x grams of 70%

0.40x+0.70(20-x)=0.52*20
0.40x-0.70x+14=10.40
-0.30x=-3.60
x=12 grams of 40% or 4.8 gms pure and 
20-x=8 grams of 70% or 5.6 gms pure.