HINT:
Suppose a t-shirt costs $\$x$ each and a singlet costs $\$y$ each.
If a t-shirt costs $k$ times as much as a singlet, then $$x=ky$$
If $\$m$ can buy $A$ t-shirts and $B$ singlets, then $$Ax+By=m$$
HINT:
Suppose a t-shirt costs $\$x$ each and a singlet costs $\$y$ each.
If a t-shirt costs $k$ times as much as a singlet, then $$x=ky$$
If $\$m$ can buy $A$ t-shirts and $B$ singlets, then $$Ax+By=m$$