Răspuns: a = 2
Explicatie pas cu pas:
1 215 - [ 130 + ( 11 × 3 + 15 × a ) ] × 5 = 250
[ 130 + ( 33 + 15 × a) ] × 5 = 1 215 - 250
[ 130 + ( 33 + 15 × a) ] × 5 = 965
130 + ( 33 + 15 × a) = 965 : 5
130 + ( 33 + 15 × a) = 193
33 + 15 × a = 193 - 130
33 + 15 × a = 63
15 × a = 63 - 33
15 × a = 30
a = 30 : 15
a = 2 → numarul, aflat prin metoda mersului invers
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Verific:
1 215 - [ 130 + ( 33 + 15 × 2 )] × 5 = 250
= 1215 - ( 130 + 63) × 5 =
= 1 215 - 193 × 5 =
= 1 215 - 965 =
= 250
