Arman need 48 minutes to mow 4 lawns with the lawns are the same size. so every 1 lawns he need time 48/4=12 minute. If he to mow 7 lawns he will take 12x7=84 minutes.
1 and 4 are not. The coefficients don't have to be integers, but the powers of the variables need to be positive integers. In 1, you have x^-1. in 4, you have x^(1/2).
