1/5(100x - 105y + 70) = 20x -21y + 14
Answer:
∠B ≈ 56.25°
Step-by-step explanation:
Since the triangle is right use the cosine ratio to solve for B
cosB =
=
=
, thus
B =
(
) ≈ 56.25°
Let

denote the number of minutes spent brushing his teeth, and let

be the mean and

the standard deviation for this distribution.

The z-score corresponding to this probability is approximately

, which means

Next, (note the sign change)

The corresponding z-score is approximately

, so you have

Solving the two equations for

and

, you'll find that the mean is approximately

and the standard deviation is approximately

.