Question

A number decreased by 10 at least is -5? What is the number?

Answer 1

See explanation.

Explanation:

If we say that the number we are looking for is `x`, then the task leads to the inequality:

`x-10>= -5`

This comes from the fact that decreasing a number by `10` means subtracting `10` from the number, and "is at least `-5`" means is greater than or equal to `-5` (`>=`)

To solve the inequality we have to add `10` to both sides:

`x-10+10>=-5+10`

`x>=5`

This means that all real numbers greater than or equal to `5` meet the given requirement; the set of solutions can also be written as an interval:

`x in [5;+oo)`