Answer is 46%.
Following are the calculations
Both cards have credit limits of $1000
First car has a balance of $410
So 1st card utilization is 410/1000= 0.41*100= 41%
2nd card balance is $510
So 2nd card utilization is 510/1000= 0.51= 51%
So total utilization of cards is (41% + 51%) / 2 = 46%