Răspuns:
[ 2 + 3 x ( 20 - 2 x 5 ) + a ] x 10 = 560
= [ 2 + 3 x ( 20 - 10 ) + a ] x 10 = 560
= ( 2 + 3 x 10 + a ) x 10 = 560
= ( 2 + 30 + a ) x 10 = 560
= ( 32 + a ) x 10 = 560
= 320 + 10a = 560
= 10a = 560 - 320
= 10a = 240
= 24
