Does the equation y=4.2x represent a proportional relationship

A proportional relationship is one in which two quantities vary directly with each other. We say the variable varies directly. If y=k. x then as x increases y also increases. Here k is called the constant of proportionality.

The given equation y = 4.2x is of the form y=k. x where k = 4.2 as x increases y value will also increase. The relation is called a proportional relationship.