What is the value of x x-2/5 =7 what is the value of x
2 answers:
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
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The cost of one roll of plain wrapping paper is $5 and one roll of shiny wrapping paper costs $16.
Step-by-step explanation:
Step 1; Assume that the cost of one roll of plain wrapping paper is $x and a roll of shiny wrapping paper costs $y. so we have the following equations from the given data
4x + 3y = 68, take this as equation 1.
9x + 2y = 77, take this as equation 2
Step 2; We multiply equation 1 with 2 and equation 2 with 3 so we can cancel out the variable y in both equations. By doing this we get
8x + 6y = 136, take this as equation 3,
9x + 2y = 77, this is equation 4.
If we subtract 4 from 3, we cancel out the y variable and can calculate the value of x.
-19x = -103 , x = = 5.
Step 3; Substituting this value of x in any of the previous equations we will get x's value. Here this value of y is substituted in equation 1.
4 (5) + 3y = 68, 20 + 3y = 68 , 3y = 48, y= 16.
So we have x = $5 and y = $16.