(659 874-650 094)*45/50+404 401*2 =

(659874-650094) *45/50  + 404401 *2=817604
1) 659874-650094=9780
2) 9780  *  45/50 = (9780*45) / (1*50) = (978*9) / (1*1) = 8802
3) 404401*2 = 808802
4) 8802+ 808802= 817604