Gabriella is organizing textbooks on her bookshelf. She has a Spanish textbook, a biology textbook, a history textbook, and a writing textbook. How many different ways can she line the textbooks up on her bookshelf?

24

Step-by-step explanation:

We call:

A - Spanish textbook

B - Biology t.b.

C - Histoey t.b.

D - Writing t.b.

U can have:

ABCD

ABDC

ACDB

ACBD

ADBC

ADCB

BACD

BADC

BCDA

BCAD

BDAC

BDCA

etc..

U have 6 for each letter.

6×4=24

41*67/2=1373.5

step-by-step explanation:

i just used a calculator

{x = -1/2 ,   y = -1

step-by-step explanation:

solve the following system:

{2 x + y = -2

{10 x - 3 y = -2

in the first equation, look to solve for y:

{2 x + y = -2

{10 x - 3 y = -2

subtract 2 x from both sides:

{y = -2 x - 2

{10 x - 3 y = -2

substitute y = -2 x - 2 into the second equation:

{y = -2 x - 2

{10 x - 3 (-2 x - 2) = -2

10 x - 3 (-2 x - 2) = (6 x + 6) + 10 x = 16 x + 6:

{y = -2 x - 2

{16 x + 6 = -2

in the second equation, look to solve for x:

{y = -2 x - 2

{16 x + 6 = -2

subtract 6 from both sides:

{y = -2 x - 2

{16 x = -8

divide both sides by 16:

{y = -2 x - 2

{x = -1/2

substitute x = -1/2 into the first equation:

{y = -1

{x = -1/2

collect results in alphabetical order:

answer:   {x = -1/2 ,   y = -1