Answer:
1.<u>2</u>
Step-by-step explanation:
A line over a number indicates that it is the last significant figure in a measurement.
It is difficult in ordinary typing to put a line over a digit, so I will use an underline instead.
A common rule is that the square root of a number contains the same number of significant figures as are in the number itself.
In all operations, you should carry one extra digit as a guard digit, to avoid roundoff errors.
Then,
√0.<u>9</u> = 0.<u>9</u>5
-√2.<u>7</u> = -1.<u>6</u>4
+√1.<u>7</u> = 1.<u>3</u>0
+√0.<u>4</u> = <u>0.63</u>
1.<u>2</u>4
We round off the answer to one digit past the decimal point, so the final answer is 1.<u>2</u>.