It's given that <ABC and <CBD are Complementary angles.
Sum of Complementary angles is equal to 90 degrees.
So, m<ABC + m<CBD = 90 degrees using the defination of complementary angles.
It is also given that m<ABC = 25 degrees.
Using substitution property of equality, you have 25°+ m<CBD = 90 degrees.
On subtracting 25 from both sides, we get 25-25+ m<CBD = 90-25.
m<CBD = 65 degrees.