F.4Maths. exponential function

(1) 5^x = 0.5 ... (1)
5^(-kx) = 8 ... (2)
(1) => x log 5 = log(1/2)
x log5 = log 1 - log2
x log5 = - log2
x = -log2/log5
(2) => -kx log5 = log8
-k(-log2/log5)/log5 = log2^3
klog2 = 3log2
k = 3
(2) 4^(x + 2y) = 64 ... (1)
16^(2x - y) = 1 ... (2)
(1) => 4^(x + 2y) = 4^3
x + 2y = 3
2x + 4y = 6 ... (3)
(2) => 16^(2x - y) = 16^0
2x - y = 0 ... (4)
(3) - (4) => 5y = 6
y = 1.2
Sub into (4), 2x - 1.2 = 0
x = 0.6
(3) 9^(3x) = 9^(1-y) ... (1)
3^(x+y) . 9y = 9^2x ... (2)
(1) => 3x = 1 - y ... (3)
(2) => 3^(x + y) . (3^2)^y = (3^2)^2x
3^(x + y) . 3^2y = 3^4x
3^(x + y + 2y) = 3^4x
x + 3y = 4x
x = y ... (4)
Sub into (3) 3y = 1 - y
4y = 1
y = 1/4
From (4), x = 1/4