Which of the following is equivalent to 3x−4y=18?
1 answer:
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Consider the puzzle:
"I have In mind a (secret) number. When I subtract 2/5 from this number I get 7. What is the number?"
To solve such puzzles we go backwards. We got 7 after we subtracted 2/5, so if we add 2/5 to 7, we get the secret number back.
Solving an equation is solving a puzzle about a secret number, which we call "x" instead of saying "something", all the time.
going backwards, means adding, if we subtracted, or dividing, if we multiplied.
So, to solve
, we just need to add 2/5 back to x:
to add 7 and 2/5, multiply 7 by 5/5
7+2/5=7.(5/5)+2/5=35/5+2/5=37/5
Thus x= 37/5
"I have In mind a (secret) number. When I subtract 2/5 from this number I get 7. What is the number?"
To solve such puzzles we go backwards. We got 7 after we subtracted 2/5, so if we add 2/5 to 7, we get the secret number back.
Solving an equation is solving a puzzle about a secret number, which we call "x" instead of saying "something", all the time.
going backwards, means adding, if we subtracted, or dividing, if we multiplied.
So, to solve
to add 7 and 2/5, multiply 7 by 5/5
7+2/5=7.(5/5)+2/5=35/5+2/5=37/5
Thus x= 37/5