Simplify each of the following and express it in the form a + ib :

Given: $2(3+4 i)+i(5-6 i)$

Firstly, we open the brackets

$2 \times 3+2 \times 4 i+i \times 5-i \times 6 i$

$=6+8 i+5 i-6 i^{2}$

$=6+13 i-6(-1)\left[\because, i^{2}=-1\right]$

$=6+13 i+6$

$=12+13 i$