You can determine the current flowing through one of many parallel pathways by applying the current divider equation.
First, we need to consider the resistance of the pathway we want to know the current through, which we'll call R_do_want. For example, if we want to know the current through the 30 Ohm resistor, then R_do_want = 30 Ohms.
Next, we lump together the resistance of all the other pathways into one resistance we don't want to know about, R_dont_want. Neglecting the 30 Ohm resistor, R_dont_want = 80||(60 + 20) = 40 Ohms.
Now we can use the current divider equation:
I_out = I_in*R_don't_want/(R_dont_want + R_do_want)
Using our values:
I_out = 7*40/(40 + 30) = 4 A
