Answer
Brand P has the lowest price per pound of cat food ($\$0.57/pound$).
Work Step by Step
We calculate the cost of cat food per pound for each brand:
Brand N:
$\$3.75$, $\$1$ off: $\$3.75-\$1.00=\$2.75$
$\$2.75$ for $3.5$ pounds: $\$2.75\div 3.5\approx\$0.79/pound$
Brand P:
$\$5.99$, $\$2$ off: $\$5.99-\$2.00=\$3.99$
$\$3.99$ for $7$ pounds: $\$3.99\div 7\approx\$0.57/pound$
Brand R:
$\$10.79$ for $18$ pounds: $\$10.79\div 18\approx\$0.60/pound$
We see that Brand P comes out the cheapest.
