Joe had collected 20 stamps at age 6. At age 10, his collection grew to 72 stamps. Assuming linear growth, write an equation that expresses the relation between time and number of stamps.

Y = 20 + 52stamps/4yrs.

Y = 20 + 13stamps/yr.

Y = 20 + 13x.

Y = The number of stamps.
X = The number of years.