# Problems that lead to equations to solve

**Problems that lead to equations to solve**

In a formula, the arrangement is that the single variable is written on the left-hand side of the equals sign. For example,

*v* = *u* + *at*

*v* is known as the **subject of the formula**.

The all the values are provided with the exception of *v*, by substituting the values, the value of *v* will be calculated.

Similarly, if all values with the exception of *t* is provided, here we will work out the value of *t* by substituting the values and rearranging the formula to solve it.

For example, if *v* = 21, *u* = 6 and *a* = 2, what is *t?*

Substituting the into the formula gives the following equation,

21 = 6 + 2*t*

6 + 2*t =* 21 (swap both sides)

2*t =* 15 (subtract both sides with 6)

*t =* 7.5 (divide both sides with 2)