The center is (h, k) = ( -1,3)
One of the asymptotic lines- the one with a positive slope - passes through ( 1, 6) [ and the center]
So.....we can write an equation of this line.....the slope = [ 6 - 3 ] / [ 1 - - 1 ] = 3/2
So.....we can write the eqation of this line as
y = (3/2)(x - -1) + k = (3/2) ( x + 1) + 3 = (b/a) ( x - h) + k
So.....
a = 2 b = 3 h = -1 and k = 3 and their sum = 7
Here's a graph : https://www.desmos.com/calculator/lxpgxphby3