Question 168651
lets call x the number he picked on monday

tuesday = x+15
wednesday= x+15(-3)=x+12

so x+(x+15)+(x+12)=87

3x+27=87
3x=60
{{{highlight(x=20)}}} number picked on monday
{{{highlight(20+15=35)}}} picked on tuesday
{{{highlight(20+12=32)}}}picked on wednesday