Question

Sam was asked to evaluate the expression 5x+3x+20 for X = 100. Sam's work shown below. Sam's work: 5x+3x+20 = 100 8x+20 = 100 8x = 80 X = 10 What mistakes did Sam make? Help Sam to answer the question correctly.

Answer 1

Sam had to substitute 100 instead of X

5x+3x+20 =
8x + 20 =
8*100 + 20 =
800 + 20 =
820 ← answer

Answer 2

The value of given expression for x=100 is 820.

He should substitute the value of x in the given expression instead of equating it to 100.

Explanation:

The given expression is

`5x+3x+20`

Sam want to evaluate the expression 5x+3x+20 for x = 100.

Substitute x=100 in the given expression.

`5(100)+3(100)+20`

`500+300+20`

`820`

The value of given expression for x=100 is 820.

Sam make his mistake in first step. He equate the given expression to 100.

He should substitute the value of x in the given expression instead of equating it to 100.