(72x135+9x28x15):25-3500:25
=(72x135+28x135-3500):25
=((72+28)x135-3500):25
=(13500-3500):25
=10000:25=400
(72x135+9x28x15):25-3500:25
=(72x135+72x28):25-3500:25
=135x(72+28):25-3500:25
=135x100:25-3500:25
=13500:25-3500:25
=(13500-3500):25
=10000:25
=400