What you need to know

Things to remember:

  • If we add to an x we do a subtraction.
  • If we subtract from an x we do an addition.
  • If we multiply and x we do a division.
  • If we divide and x we do a multiplication.

Find the value of x so that x+5=12.

Hmmmmmmmmmmm, what does it mean to add 5 to x? Let’s look at addition with numbers.

What is 2+5?

This isn’t too difficult, you can probably just see what the answer is without having to do anything.

2+5=7

 

But now, let’s look at it on a number line.

 

 

All we do is count up 5, but what if we want to go back to the number we started with? How do we get from 7 to 2? Well, we have to subtract 5!

 

 

So, how do you think this will help us find the value of x so that x+5=12? Well, we saw that to get back to the number we started with (that is the x here) we have to subtract 5 from the number the equation is equal to.

 

x = 12-5=7

x = 7

 

So, all we had to do was the opposite of the addition, which was subtraction! This is the same addition, subtraction, division, and multiplication, we just do the opposite!

 

Find the value of x so that x-8=14.

x = 14+8=22

x = 22

 

Find the value of x so that x\times5=45.

x = 45\div5=9

x = 9

 

Find the value of x so that x\div7 =4.

x = 4\times7=28

x = 28

Example Questions

Question 1: Find the value of x so that x\times12=132.

Answer

x = 132\div12=11

 

x = 11

Question 2: Find the value of x so that x\div9=11.

Answer

x = 11\times9=99

 

x = 99