Question

sabendo que x+y=10 e que x-y=4, determine o valor de 5x+5y

Answer 1

x+y=10
x-y=4

2x=14
x=14/2
x=7 

7+y=10
y=10-7
y=3

5x+5y

5.7+5.3= 35+15 = 50 

Answer 2

x = 8 y = 2 5x+5y= 50