A local sporting event charges $6 for each adult ticket and $3.50 for each child ticket. If the stadium sold a total of 65 adult and children's tickets for a total of $340, how many adult tickets were sold?

45 adult tickets were sold.

adult tickets = a

childrens tickets = b

a + b = 65

6a + 3.5b = 340

Subtract a from the equation on top to get b = 65 - a

Substitute into the second equation 6a + 3.5 (65 - a) = 340

Simplify to make 6a + 227.5 - 3.5a = 340

6a - 3.5a = 340 - 227.5

Combine like terms so that 2.5a = 112.5

Divide both sides by 2.5 to isolate the variable a

Your final answer is a = 45