Question

A 2 pound box of salt sells for $.89 and a 5 pound box sells for 2.09. What is the linear equation for this?

Answer 1

Y = ax + b;

0.89 = a * 2 + b and 2.09 = a * 5 + b =>
=> 2.09 - 0.89 = a * 5 + a * 2 + b - b => 1.20 = 3 * a => a = 1.20 / 3 => a = 0.40;
b = 0.89 - 0.40 * 2 => b = 0.89 - 0.80 => b = 0.09;

y = 0.40x + 0.09 => 0.40x - y + 0.09 = 0 is the linear equation.