Question

answer attempt 1 out of 2

Explanation:

Step1: Use triangle angle sum theorem

The sum of angles in a triangle is \(180^{\circ}\). So, \(42^{\circ}+78^{\circ}+(4x)^{\circ}=180^{\circ}\).

Step2: Simplify the left - hand side

\(42 + 78+4x=180\), which simplifies to \(120 + 4x=180\).

Step3: Solve for \(x\)

Subtract \(120\) from both sides: \(4x=180 - 120\), so \(4x = 60\). Then divide both sides by \(4\): \(x=\frac{60}{4}=15\).

Answer:

\(15\)