Solve the simultaneous equations 2x + 7y = 15 and 3x + 6y = 21

Find the lowest common multiple of 2 and 3, which is 6. Multiply each term in the first equation by 3, and each term in the second equation by 2 to produce two equations with the same coefficient of x (which is 6). The two resulting equations are 6x + 21y = 45 and 6x + 12y = 42. Now you need to cancel the x term by subtracting the second equation from the first which leaves you with 9y = 3, y =1/3. Now sub y=1/3 into any of the four equations to find an x value of 19/3.
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