15. a. Write an expression that uses both multiplication and addition (or subtraction) to describe the total fraction of Figure 5.7 that is shaded. (For example, 5/7·2/9+1/3 is an expression that uses both multiplication and addition.) Explain your reasoning. Then determine what fraction of the figure is shaded (in simplest form). You may assume that lengths appearing to be equal really are equal. b. Draw a figure in which you shade 1/4⋅1/3+3/5⋅1/3 of the figure. Explain your reasoning, then determine what fraction of the figure is shaded (in simplest form).

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Astudent is determining the influence of different types of food on the growth rate of spiders. she feeds one group of spiders two caterpillars twice a week. the other group received similarly-sized beetles twice a week. she records the amount of time required for individuals to reach sexual maturity. her hypothesis is that the spiders feeding on caterpillars will have a faster growth rate because caterpillars have a higher protein content compared to beetles. in this experiment, what is the dependent variable? spiders assigned to different feeding groups. time required to reach sexual maturity number of prey items fed twice a week. growth rates of each group.