Similar right triangles - find the missing length

Iq scores for adults age 20 to 34 years are normally distributed according to n(120, 20). in what range does the middle 68% of people in this group score on the test?

An arc subtends a central angle measuring 7pi/4 radians what fraction of the circumference is this arc?

What is the greatest number of parts of a circle that can be formed by cutting the circle with 7 straight cuts? (note: the parts do not have to be equal in size)