Question

Evaluate each expression if a=-5,b=6 and c=2.8

$-\left|18-5c\right|$

Short answer

The absolute value of expression is $\mathbf{-}\mathbf{4}$.

Step-by-step solution

Step1- Order of evaluation

To evaluate any expression involving one operation, follow the below order of operation

• First replace the algebraic expression inside the grouping symbols like matrix brackets ($\left|\right|$) with numeric expression
• Perform the multiplication inside the bracket
• Perform the subtraction inside the bracket

• Evaluate the absolute value

Step2- Simplify the expression inside grouping symbol

To evaluate the value of given expression , simply the expression inside the bracket and then find the absolute value of expression as shown below

$\begin{array}{c}-|18-5c|=-|18-5\times 2.8|\\ =-|18-14|\\ =-\left|4\right|\end{array}$

Step3- Find the absolute value of expression inside the bracket

The absolute value of $-\left|4\right|=-4$.