Amother wants to invest 11,000 for her sons future education. she invest a portion of the money in a bank cd which earns 4% and the remainder in a savings bond that earns 7%. the total interest earned is 660.00 how much was invested into the cd

Suppose, the mother deposits x amount in bank cd and y amount in savings bond so that,
x + y = 11000
or, y = 11000 - x (1)

according to question,
4% of x + 7% of y = 660
or, 4x/100 + 7y/100 = 660
or, 4x + 7y = 66000 (2)

now substitute y in equation (2) with the value in equation (1) so we get
4x + 7(11000 -x) = 66000
or, 4x + 77000 - 7x = 66000
or, 4x - 7x = 66000 - 77000
or, -3x = -11000
or x = 11000/3
or x = 3666.67

Thus, 3666.67 is the amount invested in bank cd.