Given series is:

67, 77, 87, 97,.................up to 999 terms

This forms an AP

Now, first term a = 67

common difference d = 77 - 87 = 10

Number of terms n = 999

Now Sum = (n/2)*{2a + (n-1)d}

=> Sum = (999/2)*{2*67 + (999 - 1)10}

=> Sum = (999/2)*{134 + 998*10}

=> Sum = (999/2)*{134 + 9980}

=> Sum = (999/2)*10114

=> Sum = 999*5057

=> Sum = 5051943

So, the sum of the given series is 5051943