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)
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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