Answer: the number of blues is 42.
the number of whites is 30.
Step-by-step explanation: Let there be 'x' blues and 'y' whites then
the ratio of blues to white is 7 to 5:
x : y = 7 : 5
the number of blues exceeds the number of whites by 12
x = 12 + y
the solutions of the system of equations
x/y = 7/5
x = 12 + y
are
x = 42 blues
y = 30 whites