Respuesta :

gmany

[tex]\left\{\begin{array}{ccc}3x+4y=52\\5x+y=30&|\cdot(-4)\end{array}\right\\\underline{+\left\{\begin{array}{ccc}3x+4y=52\\-20x-4y=-120\end{array}\right}\ \ \ \ \ |add\ both\ sides\\.\ \ \ \ \ -17x=-68\ \ \ \ \ |:(-17)\\.\ \ \ \ \ \ \ \ \ \ \ \ x=4\\\\put\ the\ value\ of\ x\ to\ the\ second\ equation\\\\5(4)+y=30\\20+y=30\ \ \ \ |-20\\y=10\\\\8x-2y=8(4)-2(10)=32-20=12\\\\Answer:\ \boxed{C)\ 12}[/tex]

apologiabiology

interesting

just solve them to find x and y

3x+4y=52

5x+y=30

eliminate

eliminate y

multiply 2nd equation by -4

-20x-4y=-120

add to other equation

3x+4y=52

-20x-4y=-120 +

-17x+0y=-68


-17x=-68

divide both sides by -17

x=4

subsitute back

3x+4y=52

3(4)+4y=52

12+4y=52

minus 12 both sides

4y=40

divide both sides by 4

y=10


x=4 and y=10

subsitute

8x-2y=8(4)-2(10)=32-20=12


answer is 12

C is answer

Otras preguntas