1440-80×(20-x)=60x1440-1600+80x=6080x-160=60x80x-60x=16020x=160x=8
1440-80×(20-x)=60x1440-1600+80x=60x80ⅹ-60x=1600-144020x=160x=8
1440-80×(20-x)=60x1440-1600+80x=60x80x-160=60x80x-60x=16020x=160x=160÷20x=8