If you estimate, it's okay to not be so accurate so you just round up each of the numbers to the nearest 10 and add them up.
128 would equal 130 (The last digit is larger than 5)
239 would equal 240 (The last digit is larger than 5)
152 would equal 150 (The last digit is less than 5)
130 + 240 +150 = 520
So I believe your answer is 520!
