Responder:
Copias del libro A = 50
Copias del libro B = 70
Explicación paso a paso:
Costo por libros A = 200
Costo por libro B = 150
Sea el número de libros A = x
Número de libros B = y
Número total de libros comprados = 120
Costo total = 20,500
x + y = 120 - - - (1)
200x + 150y = 20500 - - - (2)
De 1)
x = 120 - y
Sustituya x = 120-y en (2)
200 (120 - años) + 150y = 20500
24000 - 200y + 150y = 20500
24000 - 50y = 20500
-50 años = 20500 - 24000
-50y = - 3500
y = 70
x = 120 - y
x = 120 - 70
x = 50
The equation would be x+7x+12x = 100
solving gives x=5
12×5=60
7×35
5+35+60=100
The age/answer is 60
Let the measure of the unknown angle is x °
Supplementary angles sum up to 180°. So the supplementary angle of x° will be (180 - x)°
According to the given data, measure of x is 40° less than 3 times the measure of its supplementary angle (180 - x). So we can set up the equation for this scenario as:

So the degree measure of the required angle is 125°.
A. given
b. distributive property (a(b+c)=ab+ac)
c. addition or commutative property (a+b=b+a)
d. subtraction property of equality (if a=b, then a-c=b-c)
e. division property of equality (if a=b, then a/c=b/c)
f. equality property (if a=b, then b=a)