I need help with this can someone help me I have a few other ones as well I don’t understand anyone?

x=59

Step-by-step explanation:

The sum of the interior angles of a triangle add up to 180 degrees.  That means that (x+12)+(x)+(x-9)=180 degrees in total.  If we combine the like terms (combine the xs and regular constant values), the xs add up to 3x (x+x+x) and the regular constants add up to 3 (12+-9=3).  If we rewrite this in a more simplified form, we get 3x+3=180.  Subtract 3 on both sides to get 3x=177 because we want to isolate x.  3x=177 divide 3 on both sides and we get 59.  x=59

b.an increase in a causes b to decrease

10.416 meters per second

step-by-step explanation:

distance=1 00 meters

time= 9.6 seconds in decimal form or 9 3/5 as a mixed number

average speed= 100/9.6

=10.416 meters per second or 10 52/125 as a mixed number.