Решение примера (64*125+128*75): 800*5000-(300*400+5107*800): 70

(64*125+128*75):800*5000-(300*400+5107*800):70=
=(8000+9600):800*5000-(120000+4085600):70=
=17600:800*5000-4205600:70=
=22*500-60080=
=110000-60080=
=49920