Jennifer scored 90% on the test meaning she earned 90% of the possible points on the test. There were 160 possible points on the test so she earned 160 x 0.9 = 144 points. Each question is worth 2 points so she got \( \frac{144}{2} \) = 72 questions right.

To multiply fractions, multiply the numerators together and then multiply the denominators together:

\( \frac{2}{9} \) x \( \frac{2}{9} \) = \( \frac{2 x 2}{9 x 9} \) = \( \frac{4}{81} \) = \(\frac{4}{81}\)

The number of students taking German or Spanish is 8 + 8 = 16. Of that group of 16, 4 are taking both languages so they've been counted twice (once in the German group and once in the Spanish group). Subtracting them out leaves 16 - 4 = 12 who are taking at least one language. 18 - 12 = 6 students who are not taking either language.

The area of a circle is given by the formula A = πr² where r is the radius of the circle. The radius of a circle is its diameter divided by two so A = π(\( \frac{d}{2} \))². If the diameter of the logo increases by 50% the radius (and, consequently, the total area) increases by \( \frac{50\text{%}}{2} \) = 25%

To find the average of these 4 numbers add them together then divide by 4:

\( \frac{13 + 7 + 12 + 8}{4} \) = \( \frac{40}{4} \) = 10