Find the area of the rectangle or triangle.

A triangle is a closed figure bounded by three line segments.

The area of a closed plane figure is the measure of the region (surface) by its boundary.

Area of Triangle = $\frac{1}{2} · \text{base} · \text{height}$square unit

Suppose a, b, and c is three real numbers.

Distributive Property of Multiplication

Property: $\text{a} \text{(b} \text{+} \text{c} \text{)} = \text{a} · \text{b} + \text{a} · \text{c}$

Example: $\text{12} \text{(3} \text{+} \text{4} \text{)} = \text{12} · \text{3} + \text{12} · \text{4} = 36 + 48 = 84$

In this figure the base is 18 and height = 5a + 7

We know that area of Triangle =$\frac{1}{2} · \text{base} · \text{height}$

Find the area, using the distributive method of multiplication.

Property: $\text{a} \text{(b} \text{+} \text{c} \text{)} = \text{a} · \text{b} + \text{a} · \text{c}$

Area =$\frac{1}{2} · \text{18} · \text{(5a+7)} = 9 · \text{(5a+7) = 9} · \text{5a} \text{+} 9 · 7 = 45a + 63$square units

Area of the Triangle is 45a + 63 sq unit.