Sandra sold half of her comic books and then bought seven more. She now has eleven. How many did she begin with?
2(11-7) = ?
To find out how many comic books Sandra initially had, we can use simple algebraic reasoning.
Let's assume that Sandra initially had "x" comic books.
She sold half of them, so she would be left with (1/2) * x comic books.
After selling half, she bought seven more, so her total number of comic books became (1/2) * x + 7.
We know that this new total is equal to eleven, so we can write the equation:
(1/2) * x + 7 = 11
To solve this equation, we can start by subtracting 7 from both sides:
(1/2) * x = 11 - 7
(1/2) * x = 4
Next, we multiply both sides of the equation by 2 to eliminate the fraction:
2 * (1/2) * x = 2 * 4
x = 8
Therefore, Sandra initially had 8 comic books.