Question 998304
mix .80 and .60 to get 120 at .75 
x+y= 120 Subtract y from both sides:
x= 120-y We'll use this value for x in the formula below:
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.80x+.60y= .75(120) Substitute for x:
.80(120-y)+.60y= .75(120) Let's multiply to get rid of parenthesis:
96-.80y+60y= 90 Subtract 96 on both sides:
-.80y+60y= -6 Add on left:
-.20y= -6 Divide both sides by -.20:
y= -6/-.20 When you divide, remember that - and - = +
y= 30 grams will be at 60% and
120-30= 90 grams will be at 80%