Question

81*5=(80+1)*5=80*5+1*5=........
408*7=..................
397*4=(400-3)*4=400*4-3*4=.........................
298*4=....................................
ПОМОГИТЕ РЕШИТЬ!!!!!!!!!!!!!!

Answer 1

81*5=(80+1)*5=80*5+1*5=400+5=405
408*7=(400+8)*7=400*7+8*7=2800+56=2856
397*4=(400-3)*4=400*4-3*4=1600-12=1588
298*4=(300-2)*4=300*4-2*4=1200-8=1192