What is 5(x+17)=100?

2 Answers
Feb 22, 2018

x = 3

Explanation:

5 (x + 17) = 100

5x + 85 = 100

(* 5 xx 17 = 85)

Using algebraic manipulation:

5x = 100 - 85

5x = 15

x = 15/5

x = 3

Feb 22, 2018

x=3

Explanation:

Given: 5(x+17)=100

color(blue)("Approach 1 - shows usfull methods")

Multiply everything inside the brackets by the 5 that is outside

5x+85=100

To 'get rid' of the 85 on the left subtract color(red)(85) from BOTH sides

color(green)(5x+ubrace(85color(red)(-85))=100color(red)(-85))
color(white)("dddddd")darr
color(green)(5x+color(white)("d.d")0color(white)("d.d")=color(white)("dd")15)

To get rid of the 5 from 5x divide both sides by color(red)(5)

color(green)(5/color(red)(5) xcolor(white)("d")=color(white)("d")15/color(red)(5)

But 5/5=1 and 1xx x = x and 15/5=3 giving:

color(green)(x=3)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

color(blue)("Approach 2 - quicker as it uses less steps")

5(x+17)=100

Divide both sides by 5

x+17=20

Subtract 17 from both sides

x=3