[ATTACH=full]1797[/ATTACH] 144. S = 6(x^2) For 145(a), we let x = 1000 and solve for C. For 145(b), we let x = 2000 and solve for C. Let B = balance at the end of the month. B = 210 + 80 - 120 + 25 - (60 + 32) + 5 B = 8 You say?