Ineed with these questions also plz show work

Which is the equation of a line perpendicular to the line with the equation 3x+4y=8

Solve the system of equations using the substitution method. {y=−3x+7x=−2y−16 enter your answers in the boxes.

1. according to the internal revenue service, the mean tax refund for the year 2007 was $2,708. assume the standard deviation is $650 and that the amounts refunded follow a normal probability distribution. a. what percent of the refunds are more than $3,000? b. what percent of the refunds are more than $3,000 but less than $4,000? c. what percent of the refunds are less than $2,000?