(w+7.250)-3.250=20.870
w+7.250=20.870+3.250
w+7.250=24.120
w=24.120-7.250
w=16.870
(16.870+7.250)-3.250=20.870
20.870=20.870
25.620+(13.200-z)=30.000
13.200-z=30.000-25.620
13.200-z=4.380
z=13.200-4.380
z=8.820
25.620+13.200-8.820)=30.000
30.000=30.000