Determine the supply equation. Since y = m (x) + b, replace "m" with the slope of the supply curve and replace "b" with the y-intercept of the supply curve. For instance, a supply curve has a slope of 3 and intercepts the y-axis at 6. The formula then is Quantity Supplied = 3 (x) + 6.
Determine the demand equation. Since y = m (x) + b, replace "m" with the slope of the demand curve and replace "b" with the y-intercept of the supply curve. Demand curves are downward sloping, so the slope will be a negative number. For example, a demand curve has a slope of 4 and intercepts the y-axis at 15. The formula then is Quantity Demanded = 15 - 4 (x).
Set quantity demanded to equal quantity supplied. In our example, 6 + 3 (x) = 15 - 4 (x).
Use algebra to solve for "x". In our example, "x" equals 1.2857.