SOLUTION: Please help me with this problem, "If I collect $1 and $2 coins until I have 275 coins and I have a total of $402 how many $2 coins do I have?" I don't understand what they are ask

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Question 884197: Please help me with this problem, "If I collect $1 and $2 coins until I have 275 coins and I have a total of $402 how many $2 coins do I have?" I don't understand what they are asking me to do.
Answer by nerdybill(7384) About Me  (Show Source):
You can put this solution on YOUR website!
"If I collect $1 and $2 coins until I have 275 coins and I have a total of $402 how many $2 coins do I have?"
.
Let x = number of $1 coins
and y = number of $2 coins
.
From:"collect $1 and $2 coins until I have 275 coins" we get:
x + y = 275
From:"I have a total of $402" we get:
x + 2y = 402
.
Simultaneous equations:
x + y = 275
x + 2y = 402
.
multiply top equaion by -1 and ADD to bottom equation:
-x - y = -275
x + 2y = 402
------------------
y = 127 (number of $2 coins)
.
number of $1 coins:
x + y = 275
x + 127 = 275
x = 275 - 127
x = 148