



 
Hi Rob, Suppose that the rectangle has length L cm and width W cm. Look at the first two sentences in the question. A rectangle is three times as long as it is wide.
If the length is decreased by 2 cm and the width is increased by 3 cm, the new rectangle has an area of 42 cm.
From the first equation you know that L = 3W and thus you can substitute 3W for L in the second equation and solve for W. I hope this helps,  


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