Find the values of x and y when 3x+4y=18 and 4x+2y=14

Label equations: (a) 3x+4y=18(b) 4x+2y=14We need to be able to cancel out either the x's or the y's. The simplest choice is to double (b) so that we can cancel out the y's.2 x (b) : 8x+4y=28 (Give this a new label, (c))Cancel out the y's by subtracting (a) from (c), (we could do this the other way round but makes sense to take away the smaller numbers as this keeps the equation positive)So we have (c)-(a):8x+4y=28-(3x+4y=18)Which leaves 5x=10 (the y's have cancelled out). Then, dividing both sides by 5, we have x=2.We are not quite done yet, we still need to find out what y is. We do this by substituting our value for x into our original equations. Substituting x=2 into (a) gives:6+4y=184y=12y=3Always check this answer with the other equation (b). Substituting x=2 into (b) gives:8+2y=142y=6y=3 Great! Same answer. So x=2 and y=3.

Answered by Rosie E. Maths tutor

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