Can someone me how to write the equations of this three problems?

Number 11:

(356-50) ÷ 17 = x

11.    50 +17x = 356    where x = number of months

17x = 306

x =306 / 17  = 18 months answer

12.   3x + 21 = 60

3x = 39   x = $13 answer

13.    15(x - 20) =  375

15x  - 300 = 375

15x = 675

x = $45  answer

the height of the surface increases from the center out to the sides of the road.

step-by-step explanation:

as we move out we move away from the x-axis.

and as mentioned in the problem statement that height of a road increases when we move away from the center x.

hence proved that 3rd option

the height of the surface increases from the center out to the sides of the road.

is the correct option.