Question

perimeter = 42cm
5x + 3

Explanation:

Step1: Recall perimeter formula for square

The perimeter $P$ of a square is $P = 4s$, where $s$ is the side - length. Here $s=5x + 3$ and $P = 42$. So we have the equation $4(5x + 3)=42$.

Step2: Expand the left - hand side

Using the distributive property $a(b + c)=ab+ac$, we get $4\times5x+4\times3 = 42$, which simplifies to $20x+12 = 42$.

Step3: Isolate the term with $x$

Subtract 12 from both sides of the equation: $20x+12 - 12=42 - 12$, resulting in $20x=30$.

Step4: Solve for $x$

Divide both sides by 20: $x=\frac{30}{20}=\frac{3}{2}$.

Answer:

$x = \frac{3}{2}$