the sum of 12 and a number/n
138° + w° = 180° (sum of angle on a straight line)
w° = 180° - 138°
w = 42
19° + x° + w° = 90°
sub. in w=42,
19° + x° + 42° = 90°
x° = 90° - 19° - 42°
x° = 29°
x = 29
A^-b is the same as 1/a^b.
When there is a negative power, place the number and power over 1.
a^b/a^c = a^(b-c).
c is a negative power, because it is being divided, and is underneath b, which is a positive (and so it stays in the numerator).
a^c/b^c = (a/b)^c
Inside this one, the power of c is distributed to all numbers inside the parenthesis, in this case a and b.
hope this helps
D. After 150 minutes, the 5 cent one is more.
Hope this helps!