Question

WHATS X AND WHY URGENT !!!!!!

4x + 7.8y = 7.85
- 8x - y = -4.75

Answer 1

x=0.5, y=0.75

Explanation:

Method : Substitution Method

`\begin{bmatrix}4x+7.8y=7.85\\ -8x-y=-4.75\end{bmatrix}\\\\`

Isolate in for 4x +7.8y=7.85 and solve

`4x+7.8y=7.85\\\mathrm{Multiply\:both\:sides\:by\:}100\\\\4x*\:100+7.8y*\:100=7.85*\:100\\\\Refine\\400x+780y=785\\\\\mathrm{Subtract\:}780y\mathrm{\:from\:both\:sides}\\400x+780y-780y=785-780y\\\\Simplify\\400x=785-780y\\\\\mathrm{Divide\:both\:sides\:by\:}400\\(400x)/(400)=(785)/(400)-(780y)/(400)\\\\Simplify\\x =(157-156y)/(80)\\\\\mathrm{Substitute\:}x=(157-156y)/(80)\\\\\begin{bmatrix}-8*(157-156y)/(80)-y=-4.75\end{bmatrix}`

`Simplify\\\\\begin{bmatrix}(-157+146y)/(10)=-4.75\end{bmatrix}\\\\Isolate\:y \:for \:(-157+146y)/(10)=-4.75\\\\\mathrm{Multiply\:both\:sides\:by\:}10\\(10\left(-157+146y\right))/(10)=10\left(-4.75\right)\\\\-157+146y=-47.5\\\\-157+146y+157=-47.5+157\\\\Simplify\\146y=109.5\\\\\mathrm{Divide\:both\:sides\:by\:}146\\(146y)/(146)=(109.5)/(146)\\\\Simplify\\y=0.75\\\\\mathrm{For\:}x=(157-156y)/(80)\\\\\mathrm{Substitute\:}y=0.75\\\\x=(157-156*\:0.75)/(80)\\\\x=0.5,\:y=0.75`

Answer 2

X=.5, y=.75

Explanation: