Привести к общему знаменателю 7 класс
2
____
3(n_5) и

1
____
2(n+5)


2) a
______и
2(b+1)

x
____
3(1+b)

1) НОЗ: 6(n-5)(n+5)
2 / 3(n-5) = 2*2(n+5) / 6(n-5)(n+5) = 4n+20 / 6(n-5)(n+5)
1 / 2(n+5) = 3(n-5) / 6(n-5)(n+5) = 3n-15 / 6(n-5)(n+5)

2) НОЗ: 6(b+1)
a / 2(b+1) = 3a / 6(b+1)
x / 3(1+b) = 2x / 6(b+1)