Răspuns:
Explicație pas cu pas:
( 3 + a ) × 5 × 2 = 60
( 3 + a ) × 10 = 60
3 + a = 60 : 10
3 + a = 6
a = 6 - 3
a = 3
______________
( 2 + a ) × 2 × 4 = 24
( 2 + a ) × 8 = 24 ( inmultirea este asociativa )
2 + a = 24 : 8
2 + a = 3
a = 3 - 2
a = 1
_______________
2 × 3 × ( 3 + a ) = 54
6 × ( 3 + a ) = 54
3 + a = 54 : 6
3 + a = 9
a = 9 - 3
a = 6
________________
3 × 3 × ( a + 3 ) = 81
9 × ( a + 3 ) = 81
a + 3 = 81 : 9
a + 3 = 9
a = 9 - 3
a = 6
