Question 711566
X+Y=350
OR 
X=350-Y
.80X+.60Y=230
.80(350-Y)+.60Y=230
280-.80Y+.60Y=230
-.20Y=230-280
-.20Y=-50
Y=-50/-.20
Y=250 CUPS OF $.60 COFFEE WAS SOLD.
X+250=350
X=350-250
X=100 CUPS OF $.80 COFFEE.
PROOF:
.80*100+.60*250=230
80+150=230
230=230