What's the solution of -x+y=1 x+y =11 using elimination of addition and subtraction

Acompany is testing in comparing to lightbulb designs the box plot shows the number of hours that each lightbulb design last before burning out which statement is best supported by the information of the plot

Evaluate-27 ^4/3/8 a) - 81/16 b) 81/16 c) 16/81

Look at arnold's attempt to solve the equation for b: 3b = 12 b = 3 · 12 b = 36 describe the mistake that arnold made.