If seven integers are selected from the first 12 negative integers, how many pairs of these integers will have a sum of −13?

At least 1, possibly as many as 3.

There are 6 pairs of integers among those from -1 to -12 that will sum to -13. If you choose 7 integers, you may only choose one pair, or you may choose as many as three pairs.

One to three pairs will sum to -13.

the image of (6, 9) under a dilation is (4, 6). the scale factor is

225x²+4=0

225x²=0-4

225x²=-4

x²=-4/225

x=±√-4/225