Question

x+y=10 substituição y=x+4

Answer 1

x+y=10
x+(x+4)=10
2x+4=10
2x=10-4
2x=6
x=6/2
x=3

y=x+4
y=3+4
y=7

resposta: {3,7}

Answer 2

x + y = 10
y = x + 4
========
x + y = 10
x + x + 4 = 10
x + x = 10 - 4
2x = 6
x = 6/2
x = 3

y = x + 4
y = 3 + 4
y = 7


S={ 3, 7 }