(1 + x) + (2 + x) + (3 + x) + (4 + x) + (5 + x) = 10.5
15 + 5.x = 50
5.x = 50 - 15
5.x = 35
x = 35 : 5
x = 7
dấu chấm là dấu nhân
(1+x)+(2+x)+(3+x)+(4+x)+(5+x)=10\(\times\)5
=>1+2+3+4+5+5\(\times\)x=50
=>15+5\(\times\)x=50
=>5\(\times\)x=50-15
=>5\(\times\)x=35
=>x=35:5
=>x=7
Vậy x=7