You were extremely close to getting the answer for #4.
The question asks you to round the number 125.638 to the nearest hundredth.
The number 3 is in the hundredth spot, so you rounded the entire figure to 125.63
But, this is incorrect due to the rules of rounding. When rounding, if the number after the number you are rounding to is less than five, you keep the preceding number the same, but if the number is greater than 5, you round up the preceding number.
Therefore, 125.638 would round to 125.64 when rounded to the nearest hundredth.