Algebra · Junior Cert
Solving Equations
Junior Cert Higher · Linear & simultaneous equations · Tap NEXT to begin
Section 1 of 3
Linear Equations
Do the same thing to both sides until the letter is on its own.
Worked example — one step at a time
Solve $3x + 5 = 20$.
$3x = 15$
$x = 5$
$x = 5$
Worked example — with a bracket
Solve $2(x - 3) = 10$.
$2x - 6 = 10$
$2x = 16$
$x = 8$
Worked example — letters on both sides
Solve $5x - 3 = 2x + 9$.
$5x - 2x = 9 + 3$
$3x = 12$
$x = 4$
Section 2 of 3
Equations with Fractions
Now you try
You try
Solve $\dfrac{x}{2} + 3 = 7$.
Pen and paper out — try it before you reveal.
$\dfrac{x}{2} = 4$
$x = 8$
$x = 8$
$x = 8$
Section 3 of 3
Simultaneous Equations
Two equations, two unknowns. Add or subtract to cancel one letter, solve, then back-substitute.
You try
Solve $x + y = 7$ and $x - y = 3$.
Pen and paper out — try it before you reveal.
Add the equations: $2x = 10 \Rightarrow x = 5$
Sub back: $5 + y = 7 \Rightarrow y = 2$
$x = 5,\ y = 2$
$x = 5,\ y = 2$
You try
Solve $2x + y = 8$ and $x - y = 1$.
Pen and paper out — try it before you reveal.
Add: $3x = 9 \Rightarrow x = 3$
$3 - y = 1 \Rightarrow y = 2$
$x = 3,\ y = 2$
$x = 3,\ y = 2$
That’s Solving Equations.
Linear equations, ones with fractions, and simultaneous equations by elimination.