Find the perimeter of a rectangle with a length of 10m+2 and a width of 5m I guessed the answer and got it correct I just need an explanation please help

30m+4
PLEASE HELP

Solve the given system of equations. 2y= -x+9 , 3x-6= -15

Evaluate this using ! 0.25^2 x 2.4 + 0.25 x 2.4^2 − 0.25 x 2.4 x 0.65

Scores on a university exam are normally distributed with a mean of 78 and a standard deviation of 8. the professor teaching the class declares that a score of 70 or higher is required for a grade of at least “c.” using the 68-95-99.7 rule, what percentage of students failed to earn a grade of at least “c”?