Question

How do you solve `b/2 - b/5 =6`?

Answer 1

`b=20`

Takes longer to explain than do the actual maths.

Explanation:

Multiply by 1 and you do not change the overall value. However, 1 comes in many forms so you can change the way a number looks without changing its overall value.

`" "color(green)([b/2color(red)(xx1)]" "-" "[b/5color(red)(xx1)]=6)`

`" "color(green)([b/2color(red)(xx5/5)]" "-" "[b/5color(red)(xx2/2)]=6)`

`" "[(5b)/10]" "-" "[(2b)/10]" " = 6`

`" "(3b)/10" "=" "6`

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Multiply both sides by `color(red)(" " 10)`

`" "color(green)(color(red)(10xx)(3b)/10" "=" "color(red)(10xx)6 )`

`" "10/10xx3b" "=" "60`

`color(white)(.)`

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But `10/10=1`

`" "3b" "=" "60`

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Divide both sides by 3

`" "b" "=" "20`