Answer:
Step-by-step explanation:
Method : Substitution Method
[tex]\begin{bmatrix}4x+7.8y=7.85\\ -8x-y=-4.75\end{bmatrix}\\\\[/tex]
Isolate in for 4x +7.8y=7.85 and solve
[tex]4x+7.8y=7.85\\\mathrm{Multiply\:both\:sides\:by\:}100\\\\4x\times\:100+7.8y\times\:100=7.85\times\: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\\\frac{400x}{400}=\frac{785}{400}-\frac{780y}{400}\\\\Simplify\\x =\frac{157-156y}{80}\\\\\mathrm{Substitute\:}x=\frac{157-156y}{80}\\\\\begin{bmatrix}-8\times\frac{157-156y}{80}-y=-4.75\end{bmatrix}[/tex]
[tex]Simplify\\\\\begin{bmatrix}\frac{-157+146y}{10}=-4.75\end{bmatrix}\\\\Isolate\:y \:for \:\frac{-157+146y}{10}=-4.75\\\\\mathrm{Multiply\:both\:sides\:by\:}10\\\frac{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\\\frac{146y}{146}=\frac{109.5}{146}\\\\Simplify\\y=0.75\\\\\mathrm{For\:}x=\frac{157-156y}{80}\\\\\mathrm{Substitute\:}y=0.75\\\\x=\frac{157-156\times\:0.75}{80}\\\\x=0.5,\:y=0.75[/tex]
