9x - 21y = 30
-3x+7y=-10
how to solve by substitution

Valentina is subtracting from . she finds the lcd to be 15y2. what is valentina's next step?

Prove that quadrilateral is a rhombus.

The american academy of pediatrics wants to conduct a survey of recently graduated family practitioners to assess why they did not choose pediatrics for their specialization. provide a definition of the population, suggest a sampling frame, and indicate the appropriate sampling unit.