Atextbook store sold a combined total of 231 psychology and biology in a week. the number of psychology textbook sold was two times the number of biology textbook sold. how many textbook of each type were sold.

the number of psychology textbook sold that week is 154.

the number of biology textbook sold that week is 77

Step-by-step explanation:

Let x represent the number of psychology textbook sold in a week.

Let y represent the number of biology textbook sold in a week.

A textbook store sold a combined total of 231 psychology and biology in a week. This means that

x + y = 231 - - - - - - - - - - - - 1

The number of psychology textbook sold was two times the number of biology textbook sold. This means that

x = 2y

Substituting x = 2y into equation 1, it becomes

2y + y = 231

3y = 231

y = 231/3 = 77

Substituting y = 77 into x = 2y, it becomes

x = 2 × 77 = 154

solve systems of equations by graphing. a system of linear equations contains two or more equations e.g. y=0.5x+2 and y=x-2. the solution of such a system is the ordered pair that is a solution to both equations. to solve a system of linear equations graphically we graph both equations in the same coordinate system

step-by-step explanation: