91Ó°ÊÓ

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

Rules of Addition/ Subtraction:

• Two numbers with similar signs 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 the 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 $3a^2−2ab+c$, substitute 2 for $a,1$for $b$, and 5 for $c$.

$3a^2−2ab+c=3{\left(2\right)}^2−2\left(2\right)\left(1\right)+5$

Further, simplify the expression by applying the rules of BODMAS.

$3a^2−2ab+c=3{\left(2\right)}^2−2\left(2\right)\left(1\right)+5$

$$\begin{gathered} =3×4−4+5 \\ =12−4+5 \\ =8+5 \\ =13 \end{gathered}$$