Alinear relation has a slope of -5 and passes through the point (-3, 228). find the value of x when y=517

First, find the equation of the line. 
the slope is given, so y=-5x+b
now use the given point to find b: 228=-5*(-3)+b, b=228-15=213

so the equation of the line is y=-5x+213

when y=517:                         517=-5x+213
                                              304=-5x
                                              x=-60.8