Please explain the difference between the meanings of the following two phrases: A. 5 less than a number
B. 5 is less than a number

5 less than is doing something like 5 less than 7 that means your doing 7-5 but with 5 is less than 7 your comparing the two so you would do 5>7

is less than is comparing

less then is subtraction

distance covered by pamela in 9 l of fuel = 99km

let us apply unitary method here.

distance covered by pamela in 1 l of fuel =99/9 =11 km

now let us find distance covered by pamela if she has 12 l of fuel.

distance covered in 12 l = distance covered in 1 l of fuel * 12

we know that distance covered by here in 1 l is 11 km.

so distance covered in 12 l of fuel = 11*12 = 132 km.

f(x) has value 150 at x= 0

and 0 at x= 3

so d(f(x))/dt = slope = -150/3 = -50