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A variable needs to be eliminated to solve the system of equations below. Choose the correct first step.

{:[-2x+10 y=72],[-6x+10 y=36]:}
Add to eliminate 
y.
Subtract to eliminate 
x.
Add to eliminate 
x.
Subtract to eliminate y.

A variable needs to be eliminated to solve the system of equations below. Choose the correct first step.\newline2x+10y=726x+10y=36 \begin{array}{l} -2 x+10 y=72 \\ -6 x+10 y=36 \end{array} \newlineAdd to eliminate y \mathbf{y} .\newlineSubtract to eliminate x \mathbf{x} .\newlineAdd to eliminate x \mathbf{x} .\newlineSubtract to eliminate y.

Full solution

Q. A variable needs to be eliminated to solve the system of equations below. Choose the correct first step.\newline2x+10y=726x+10y=36 \begin{array}{l} -2 x+10 y=72 \\ -6 x+10 y=36 \end{array} \newlineAdd to eliminate y \mathbf{y} .\newlineSubtract to eliminate x \mathbf{x} .\newlineAdd to eliminate x \mathbf{x} .\newlineSubtract to eliminate y.
  1. Analyze Coefficients: Analyze the coefficients of the variables in both equations.\newlineWe have the system of equations:\newline2x+10y=72-2x + 10y = 72\newline6x+10y=36-6x + 10y = 36\newlineTo eliminate a variable, we need to make the coefficients of either xx or yy the same with opposite signs so that addition or subtraction will cancel out that variable.
  2. Compare Coefficients: Compare the coefficients of xx and yy in both equations.\newlineThe coefficients of yy are already the same (1010 and 1010), but the coefficients of xx are not the same (2-2 and 6-6). To eliminate yy, we would need to multiply the first equation by a factor that would make the coefficient of yy in the first equation the opposite of the coefficient of yy in the second equation. However, since the coefficients of yy are already the same, we can simply subtract one equation from the other to eliminate yy.
  3. Decide Operation: Decide on the operation to eliminate yy. Since the coefficients of yy are the same, we can subtract the second equation from the first to eliminate yy. 2x+10y=72-2x + 10y = 72 - (6x+10y=36)(-6x + 10y = 36) This will result in: 2x+10y(6x+10y)=7236-2x + 10y - (-6x + 10y) = 72 - 36
  4. Perform Subtraction: Perform the subtraction to check if yy is eliminated.2x+10y(6x+10y)=7236-2x + 10y - (-6x + 10y) = 72 - 36 simplifies to:2x+10y+6x10y=7236-2x + 10y + 6x - 10y = 72 - 36 The terms +10y+10y and 10y-10y cancel each other out, leaving:4x=364x = 36