17. The equation x^2+ y^2 - 12x + 10y = t describes a circle. Algebraically find the center of the circle.

Change the mixed fractions to an improper fraction.
4 5/7 = 32/7
1 6/7 = 13/7

Now you can easily subtract since both fractions have common denominators
32/7 - 13/7
(Think: 32 - 13 = 19)

Change the improper fraction to a mixed fraction
19/7 = 2 5/7

2 5/7

Hope I helped =)