# Make Equations

Make an equation! Many problems can be solved by using equations. Determine what the unknown part is. Call it $x$. Arrange the rest of the information based on what you named $x$.

Jasmine, Martin and Qiang are 37 years in total. Martin is four years older than Jasmine. Qiang is three years younger than Jasmine. How old are they?

You can make an equation where all the ages are expressed through the age of Jasmine.

$\text{Jasmine} + \text{Martin} + \text{Qiang} = 37$

\begin{aligned} \text{Jasmine} &= x \\ \text{Martin} &= \text{Jasmine} + 4 = x + 4 \\ \text{Qiang} &= \text{Jasmine} - 3 = x - 3 \end{aligned}

You can now replace the expressions in the equation above:

\begin{aligned} \text{Jasmine} + \text{Martin} + \text{Qiang} &= 37 \\ x + 4 + x + x – 3 &= 37 \\ 3x + 1 &= 37 \\ 3x &= 36 \\ x &= 12 \end{aligned}

So,

• Jasmine is 12 years old,
• Martin is 12 + 4 = 16 years old,
• Qiang is 12 – 3 = 9 years old.