Bantuin ya kakak:)))

3.) 1/x = 1/12 + 1/18
1/x = 3/36 + 2/36
1/x = 5/36
x = 36/5
x = 7,2hari

4.)
4 : (a + 2) = 6 : (2a - 1)
4/(a + 2) = 6 / (2a - 1)
4×(2a - 1) = 6×(a + 2)
8a - 4 = 6a + 12
8a - 6a = 12 + 4
2a = 14
a = 14/2
a = 7