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f(c) means let x=c. Remember that c is just an unknown number.

The expression f(c)=9 means that when we put c through the function f(x)=7-4x, it gives the answer 9. Therefore we know 7-4c...

The easiest way to solve simultaneous equations is to label the equations so you clearly follow them throughout.

For example, say you are asked to solve the unknowns for the simultaneous ...

When solving a quadratic equation like this it is useful to write it in the form (x+a)(x+b)=0, as this is simply saying 'two numbers multiplied together equal zero'. A general rule in maths is that whenev...

First label all the sides with letters:longest side = amiddle length side = bshortest side = cNow convert the question into equation form: "the longest side is two units more than the shortest side&q...

Prices are: £40 per guest. Total cost reduced by 5% with over 60 guests. 

First, we work out the cost of Nisha's suggestion.

£40 x 70 guests = 2800

To find 5% ...