a+1+a+2+a+3+a+4+a+5=65
(a+a+a+a+a )+ ( 1+2+3+4+5 ) = 65
a x 5 +15 = 65
a x 5 = 65 -15
a x 5 = 50
a = 50 :5
a = 10 ai k mk mk tk lai
( a + 1 ) + ( a + 2 ) + ( a + 3 ) + ( a + 4 ) + ( a + 5 ) = 65
a x 5 + ( 1 + 2 + 3 + 4 + 5 ) = 65
a x 5 + 15 = 65
a x 5 = 65 - 15
a x 5 = 50
=> a = 10 .