Anumber was written on the board. one student increased the number by 23, but another student decreased the number by 1. the first student's result was 7 times greater than the result of the second student. what is the number written on the board?

Let the number be x.

First student increased the number by 23, therefore
⇒ x + 23

Second student decreased the number by 1, therefore
⇒ x - 1

The first student's result was 7 times greater than the result of the second student's, therefore
⇒ x + 23 = 7(x - 1)


Solve for x:

x + 23 = 7( x- 1)
x + 23 = 7x - 7
6x = 30
x = 5


The  number on the board is 5.

Planet earth has a mass of 5.9726x10²⁴ kg.then: 5.9726x10²⁴ kg=100% of the total earth mass.if the water´s mass=5x10-4 % of the total mass, we can solve this problem by the rule of three.5.9726x10²⁴ %*10⁻⁴ %x=(5.9726x10²³ kg)(5*10⁻⁴  %) / 100 %=2.9863x10¹⁹ kganswer:   the mass of the planet´s water would be   2.9863 x 10¹⁹ kg.