Răspuns:
Explicație pas cu pas:
100x (84-[87-(7xx-9): 2]}-10=2390
100x (84-[87-(7xx-9): 2]}=2390+10=2400
84-[87-(7xx-9): 2]}=2400:100=24
84-[87-(7xx-9): 2]=24
[87-(7xx-9): 2] =84-24=60
[87-(7xx-9): 2]=60
87-60=(7xx-9): 2
27*2=7*x-9
54+9=7x
63=7x
x=63/7=9