Pleas help fill out the blank for statements and reasons!!!

Solve the system of equations y= 3/2 - 1, -x+ y =-3

Lines a and b are perpendicular. if the slope of line a is 3, what is the slope of line b?

$30 to spend on dinner tax and gratuity at mos restaurant rax is 6% and they give a 15% tip on the total bill after taxes thier dinner cost $21 which statement correctly explains wether andrew and kate have enough money to pay their bill