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Lucy paid a total of $550 for a brooch, a necklace and a watch.
She spent 3/5 money on the brooch. The necklace cost 3 times as much as the watch.
How much did she pay for the necklace?
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To simplify the problem, subtract the cost of the broch from $550.
The rest is 2/5 of $550, which is $220.
So, the necklace and the watch cost together $220, and the necklace costs 3 times as much as the watch.
From it, using your mental skills, you conclude that the necklace costs 3/4 of $220, or 3*55 = 165 dollars. ANSWER
Alternatively, if you rely more to equations than on your mental skills,
you can write x + 3x = 220 and solve it for x, which is the price for the watch.
Doing this way, you get that the watch costs x= 55 dollars and the necklace costs 3x = 3*55 = 165 dollars,
giving the same answer.
Solved.