I need answers for a and b please

Multiply. write your answer in simplest form. 3/8 x 5/7

An energy drink company claims that its product increases students' memory levels. to support its claims, the company issues advertisements claiming that 8 out of 10 people (chosen randomly from across the country) who tried their product reported improved memory. the missing component in this study is a .

Asystem of equations has 1 solution.if 4x-y=5 is one of the equations , which could be the other equation ?