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Remember that we have two values here, the price of the washing machine BEFORE and the price AFTER the 20% VAT increase. The value AFTER the increase is 600. To get to the value before, you can't simply s...

a : c = 4 : 5 and b : c = 2 : 3 so getting a common value of 15 for B gives a : c = 12 : 15 and b : c = 10 : 15  we can now compare these ratios and get 12 : 10 : 15 this is not divisible by any common f...

x = 4.5y = -1.5To answer this question, first, rearrange the first equation to make y the subject: 5x + y = 21 --> y = 21 - 5xYou can now substitute this value of y into the second equation: x - 3(21 -...

Via inspection, one can factorise this via the difference of squares; since a^2-b^2 = (a+b)(a-b), therefore:100-x^2 = (10-x)(10+x)

The first step whenever you are given an equation is to group like terms. By this I mean put all the terms with the same letter next to it together and, in this case, the numbers without a letter. For the...