Jen Planted a 7 ft tee, tree grows 3 ft each year. Now tree is 4times original height. How many year ago was tree planted.

Is the equation y=3x+7 right, where y= 7*4 and x= no of years

Yes

y = 3 x + 7 = 4 * 7 = 28

3 x + 7 = 28

3 x = 28 - 7 = 21

x = 21 / 3 = 7 yrs

7 ft + 7 * 3 ft = 7 ft + 21 ft = 28 ft = 4 * 7 ft