In right ∆abc, c is a right angle and sin a = 243/312. what is mb?

The sin of any given angle is:
sin(∅) = perpendicular / hypotenuse

The perpendicular of angle A will be equivalent to the base of angle B. Therefore,
Cos(B) = 243/312
B = Cos⁻¹(243/312)
B = 38.8°

The measure of angle B is 38.8 degrees.

Not Sure Without Slope

Step-by-step explanation:

you could use the formula y-y1=m(x-x1)(point slope form) where m is the slope, y1 is the first y point and x1 is the first x point.

For example if a line has slope 3 and passes through the points (5, 6), then the formula you would solve is y-6=3(x-5) to find the equation of the line in slope-intercept form and you should know what to do with everything else.