First, we convert everything to inches and solve for the width, w:
[tex]2w + 2(w + 54) - 30 = 750\\2w + 2w + 108 - 30 = 750\\4w = 612\\w = 153[/tex]
Then, solve for the length:
[tex]l = w + 54\\l = 153 + 54\\l = 207[/tex]
Then, convert back to feet if necessary:
[tex]w = 153/12 = 12.75\\l = 207/12 = 17.25[/tex]
You can calculate the area easily now (w * l)