The equation for a line in slope-intercept from is y = mx + b where m is the slope and b is the y-intercept.
Plug in our given information:
y = - 1/4x + b
To find b, plug in our given ordered pair:
3 = - 1/4(- 5) + b
3 = 5/4 + b
Subtract 5/4 from both sides to isolate the variable B
3 - 5/4 = b
12/4 - 5/4 = b
7/4 = b
Your equation is y = - 1/4x + 7/4