Answer:
Plan A last 0.75 hours or 45 minutes.
Plan B last 1.5 hours or 90 minutes.
Step-by-step explanation:
Let [tex]a[/tex] be the number of hours that the plan A last, an [tex]b[/tex] the number of hours of plan B. Then for the Wednesday you have:
[tex]2a+3b=6[/tex]
And for the Thursday is:
[tex]6a+5b=12[/tex]
Multiply the equation of Wednesday by -3:
[tex]-6a-9b=-18[/tex]
Using the method of addition using this last equation and the equation of Thursday
[tex]-6a-9b=-18\\6a+5b=12\\--------\\-4b=-6\\b=\frac{-6}{-4}\\b=1.5 hours[/tex]
Replacing the value of [tex]b[/tex] in one of the equations
[tex]6a+5b=12\\6a+5(1.5)=12\\6a+7.5=12\\6a=12-7.5\\a=\frac{4.5}{6} \\a=0.75hours[/tex]