Double slit, with yellow and blue light please help

A double slit with a spacing of 0.0716 mm between the slits is 2.96 m from a screen.
If yellow light of wavelength 554 nm strikes the double slit, what is the separation between
the zeroth- and first-order maxima on the screen?
Answer in units of m.

If blue light of wavelength 425 nm strikes the
double slit, what is the separation between
the second- and fourth-order maxima?
Answer in units of m.

Yellow light:
make the spacing between slits variable D, the distance from the screen variable L, the distance between two maxima variable X, the wavelength variable λ.

for maxima the equation using the small angle approximation is λ = D * X / L

simply solving for X:
X = λ * L / D = (554x10^-9m) (2.96m) / (.0716x10^-3m) = .02290m


Blue light:
Using the same strategy and variables:
X = (425x10^-9m) (2.96m) / (.0716x10^-3m) = .01757m

now keep in mind X is the distance between 2 maxima, but in this case we are going from the 2nd to the 3rd to the 4th maximum, so just multiply X by 2

2 * X = 2 * (.01757m) = .0351m

wavelength = 554 nm = 554 * 10 ^ -9 m
n = 1
d = 0.0716 mm (awfully small). = 7.16 * 10 ^ -2 mm [ 1m / 1000 m] = 7.16 * 10^-5 m
L = 2.96 m
x = ???

wavelength = x*d / n*L
x = wavelength * n * L / d

x = 554 * 10^-9 m *1 * 2.96/ 7.16 * 10^ - 5
x = 0.0229 m
x = 2.29 cm which is pretty big. You want the previous answer.

Problem 2
=======
x = wavelength * n * L / d
x = 425 * 10^-9 * 2.96 ( 4 - 2 ) / 7.16 * 10^-5
x = 0.0351 m