Question

gente é pra amanha mim ajudem

Answer 1

2x + y = 4
x + 3y = 8

x = 8 - 3y

2x + y = 4
2.(8 - 3y) + y = 4
16 - 6y + y = 4
16 - 5y = 4
16 - 4 = 5y
12 = 5y
5y = 12
y = 12/5

x = 8 - 3y
x = 8 - 3 . 12
                 -----
                   5

x = 8 - 36
           -----
             5

5x  =    40 - 36
---       ----------
 5             5

5x = 4
x = 4/5

***********************************

3x + y = 12
x - 5y = 4

x = 4 + 5y

3x + y = 12
3.(4 + 5y) + y = 12
12 + 15y + y = 12
16y = 12 - 12
16y = 0
y = 0/16
y = 0

x = 4 + 5y
x = 4 + 5.0
x = 4

*******************************
a + b = 400
2a + 3b = 900


a + b = 400
a = 400 - b

2a + 3b = 900
2.(400 - b) + 3b = 900
800 - 2b + 3b = 900
800 + b = 900
b = 900 - 800
b = 100

a = 400 - b
a = 400 - 100
a = 300

**************************************
x + y = 100
10x + 20y = 1550 (:10)

x + y = 100
x + 2y = 155

x = 100 - y

x + 2y = 155
100 - y + 2y = 155
100 + y = 155
y = 155 - 100
y = 55

x = 100 - y
x = 100 - 55
x = 45