The curve passes through (0, -13) so -13 = a*02+b*0+c or c = -13
Hence y = ax2 + bx -13
Maximum occurs when y = 5 and x = 3, so 5 = 9a + 3b -13
or 9a + 3b = 18, or 3a + b = 6 ...(1)
The slope is given by slope = 2ax + b, and this must be zero at a maximum,
so 2a*3 + b = 0 or 6a + b = 0 ...(2)
You can use equations (1) and (2) to find a and b, then use
m = a*42 + 4b - 13 to calculate m.