Use the order of operations PEMDAS parentheses, exponents, multiplying and dividing left to right, and lastly, adding and subtracting left to right. First, parentheses. 6x8 = 48. So now we have 978 - 48 + 99. Its all adding and subtracting, so we can do it simple... 978 - 48 = 930. 930 + 99 is 1029. That's the answer.
1029
Hope this helped!