couple of assumptions here since they were not in the problem statement ...
1. interest is simple interest per annum
2. he needs $58,500 per year to support his present lifestyle
$1.5 million - $550,000 = $950,000
let x = amount of money invested at 7.5% interest
then (950,000 - x) = amount of money invested at 4.5% interest
interest earned = 58,500 = (x)(7.5%) + (950,000 - x)(4.5%)
don't forget to change the percentages to decimals ... then solve for x.