How can you do a simultaneous equation in maths?

Simultaneous Equations are very helpful because it can help u solve problems in real life. There are 2 ways to approach a simultaneous equation, Substitution and elimination method. As a good practice it is always good to practice your substitution method first. I wont go too advance for now but consider this question;
Find two numbers whose sum is 21 and difference is 9.

This question requires 2 equation to solve; thus it is call simultaneous equation.

Solve: Let x be a number, and Let y be another number.

x + y = 21 equation 1
x - y = 9 equation 2

Rearrange equation 2 to make equation 3(Equation 3 is just to sub into the other eqs)
x = 9 + y equation 3

Sub equation 3 into 1
(9 + y) + y = 21
9 + 2y = 21
2y = 12
y = 6 First solution!

Sub y = 6 into equation 2
x - 6 = 9
x = 15 Second Solution!

Therefore, the numbers are 15 and 6.

In a simultaneous equation (with 2 variable) there will always be 2 answers.

Good luck and hope this help.