Find x if YI and XJ are medians, XJ = 7x - 1 and DJ = 3x - 3 please help asap

Erin bought christmas cards for $2 each to send to her family and friends. which variable is the dependent variable?

Atype of plant is introduced into an ecosystem and quickly begins to take over. a scientist counts the number of plants after mmonths and develops the equation p(m)= 19.3(1.089)^m to model the situation. most recently, the scientist counted 138 plants.assuming there are no limiting factors to the growth of the plants, about how many months have passed since the plants werefirst introduced? a)o 6.1b)0.6.6c)10 72d)o 23.1

How are algebraic expressions evaluated using substitution?