Răspuns:
Explicație pas cu pas:
1) a - b = 64 si c = 20
a×c - b×c = c × ( a - b ) = 20 × 64 = 1 280
_________________________________
2) a + b = 29 si c = 18
a×c + b×c = c × ( a + b ) = 18 × 29 = 522
______________________________
3) x = 30
a × x + b × x = 120
x × ( a + b ) = 120
30 × ( a + b ) = 120
a + b = 120 : 30
a + b = 4