Răspuns:
Explicație pas cu pas:
3 × ( a + 7 ) = 27
a + 7 = 27 : 3
a + 7 = 9
a = 9 - 7
a = 2
______________
9 × ( a + 5 ) = 54
a + 5 = 54 : 9
a + 5 = 6
a = 6 - 5
a = 1
___________________
5 × ( 10 - a ) = 40
10 - a = 40 : 5
10 - a = 8
a = 10 - 8
a = 2
_______________
4 × ( a - 2 ) = 28
a - 2 = 28 : 4
a - 2 = 7
a = 7 + 2
a = 9