What is 39 to 1 significant figure​

Explanation

We can only keep one of the digits: either the tens digit or the units digit. If we kept only the units digit, then we go from 39 to 9 which is a very steep drop. If we kept the tens digit then we go from 39 to 30

The 0 in the "30" is not significant. It's just a placeholder to help us tell 30 apart from simply 3. The drop from 39 to 30 is much smaller (compared to from 39 to 9). But you can probably see that it's even better to bump up to 40 instead, due to the smaller change.

In short, 39 rounds up to 40 when rounding to one significant digit.

c.

step-by-step explanation:

because first you have to add the 4x, 9x, and the 7x together and you get 20x and then you add the last numbers up and you get 5and then you put the subtraction sign in there and that's how you get the answer.