91Ó°ÊÓ

• To get rid of a number in addition from one side, subtract the same number from both sides of equal sign.
• To get rid of a number in subtraction from one side, add the same number both sides of equal sign.
• To get rid of a number in multiplication from one side, divide the same number from both sides of equal sign.
• To get rid of a number in division from one side, multiply the same number both sides of equal sign.

Rules of Addition/ Subtraction:

• Two numbers with similar sign always get added and the resulting number will carry the similar sign.
• Two numbers with opposite signs always get subtracted and the resulting number will carry the sign of larger number.

Rules of Multiplication/ Division:

• The product/quotient of two similarsign numbers is always positive.
• The product/quotient of two numbers with opposite signs is always negative.

In order to calculate $\frac{a−b}{c−d}$, substitute$-3$ for a, 0 for b, 3 for c and $-1$for d.

$\frac{a−b}{c−d}=\frac{−3−0}{3−\left(−1\right)}$

Evaluate the expression in numerator and denominator.

$\begin{array}{c}\frac{a−b}{c−d}=\frac{−3−0}{3−\left(−1\right)}\\ =\frac{−3}{3+1}\\ =−\frac{3}{4}\end{array}$

Thus, the solution of the expression is $−\frac{3}{4}$.