Provincial Express charges \$4, plus \$1.50/kg, to deliver a package overnight. The Package people charges \$5, plus \$1/kg. When is Provincial Express less expensive to use?

What do you know about linear equations? This one will be of the form $y=mx+c$ where "c" is fixed cost and "m" being variable cost (in this case per kilo) and x is mass.

Provincial Express is $4+ 1.50x$ - 4 is the fixed cost and 1.5 the variable cost.