Green Bank charges a monthly fee of $3 for a checking account and $.10 per check. Savings-R-Us bank charges a $4.50 monthly fee and $.05 per check. How many checks required to be used for the monthly costs to be the similar for both banks?

Let x = the number of checks written in which month. Green Bank's fees would thus be represented by .10x + 3 and Savings-R-Us would be represented by .05x + 4.50. To ?nd out the value for which the banks charge the similar amount, set the two expressions equal to every other: .10x + 3 = .05x + 4.50. Subtract 3 from both sides: .10x + 3 - 3 = .05x + 4.50 - 3. This now becomes: .10x = .05x + 1.50. Subtract .05x from both sides of the equation: .10x - .05x = .05x - .05x + 1.50; this simpli?es to: .05x = .05x/150 = 1.50. Divide both sides of the equation by .05: .05/.05 = 150/.05. The variable is now alone: x = 30. Costs would be the similar if 30 checks were written.