Look at the problem and work shown. in which line was an error made and what should have been done differently?

seven less than 5 times a number is 62. what is the number?

7 – 5n = 62 (line 1)

7 – 7 – 5n = 62 – 7 (line 2)

–5n = 55 (line 3)

–5n ÷ 5 = 55 ÷ 5 (line 4)

n = –11 (line 5)

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?