Answer :
"Fifteen less than a number" is the same as subtracting 15 from an unknown number, 'x'.
"at most" is less than or equal to.
So we have:
[tex]\sf~x-15\le6[/tex]
Add 15 to both sides:
[tex]\sf~x\le21[/tex]
"at most" is less than or equal to.
So we have:
[tex]\sf~x-15\le6[/tex]
Add 15 to both sides:
[tex]\sf~x\le21[/tex]