# Ex.4.3 Q2 Simple-Equations Solutions-Ncert Maths Class 7

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## Question

Solve the following equations.

(a) $$2(x + 4) = 12$$

(b) $$3(n\, – 5) = 21$$

(c) \begin{align}3\left( {n-5} \right) = - 21\end{align}

(d) \begin{align}- 4\left( {2 + x} \right) = 8\end{align}

(e) $$4(2 \,– x) = 8$$

## Text Solution

What is Known?

Equations.

What is unknown?

The value of the variable.

Reasoning:

To solve these equations, transpose the variables on the one side and constants on the other side, and simplify them and get the value of variable.

Steps:

(a) $$2(x + 4) = 12$$

\begin{align} 2(x + 4) &= 12\\2x + 8 &= 12\\2x &= 12 – 8\\2x &= 4\\x& = \frac{4}{2}\; \text{or} \;x = 2\end{align}

(b) $$3(n \,– 5) = 21$$

\begin{align}3(n – 5) &= 21\\3n – 15 &= 21\\3n &= 21 + 15\\3n &= 36 \\ n &= \frac{{36}}{3} \,\text{or}\, n = 12\end{align}

(c) \begin{align} 3\left( {n-{\rm{ }}5} \right) = - 21\end{align}

\begin{align} 3\left( {n-{\rm{ }}5} \right) &= - 21 \\3n \,– 15 &=\, –21\\3n &=\, –21 + 15\\3n& = \,–6\\ n &= \frac{{ - 6}}{3}\,\text{or}\, n = \,–2\end{align}

(d) \begin{align}- 4\left( {2 + x} \right) = 8\end{align}

\begin{align} - 4\left( {2 + x} \right) &= 8\\– 8 \,– 4x &= 8\\–4x &= 8 + 8\\–4x &= 16\\x = \frac{{ - 16}}{4}& = \,–\,4\end{align}

(e)  $$4(2 \,– x) = 8$$

\begin{align}4(2 – x) &= 8\\8 – 4x &= 8 \\– 4x &= 8\,– 8 = 0 \,\text{or} \,x = 0\end{align}

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