In January, rochelle purchased two bottles of children's multivitamins and three bottles of adult multivitamins. she spent $54 on that purchases write two equations to represent the cost of a bottle of children's multivitamins (c) and adult multivitamins(a). docs do not work for me

Which values for a and b will create infinitely many solutions for this system of equations? ax-y=8 2x+y=b

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'

Each person in an it department of 25 people works on at least one of 3 major projects: system security, program implementation, platform development. 10 people work on system security, 13 work on program implementation, and 12 work on platform development. 4 people work on system security and platform development, 5 people work on program implementation and platform development, and 2 people work on all three projects. how many people work on system security and program implementation?