for (int k = i + 1; k < 60; k++) { float f = a[k, i] / a[i, i]; for (int j = i + 1; j < 60; j++) a[k, j] = a[k, j] - a[i, j] * f; z[k] = z[k] - z[i] * f; } Here is the code. It shows an error on the cells of the arrays a and z: float f = a [k, i] / a [i, i]; It seems like the type float can be divided into type float. Right? Both arrays of this type. What to do to get rid of the error?