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[(2×a+178)×15+90]:45=630

Răspuns :

(2a+178)×15+90 = 630×45 = 28350
(2a+178)×15 = 28350-90 = 28260
2a+178 = 28260:15 = 1884
2a = 1884-178 = 1706
a = 1706:2 = 853