Describe weather the linear transformations in exercises $16$ through $20$ are invertible. find the inverse if it exists.

$N_1=3x_1+5x_2$

$n_2=5x_1+8x_2$

$y_1=4x+2x_1$

II$.$

$y_1=r_2$

$y_2=r_1$

$y_3=x_1$

$x_1+x_{2}t$

$x_2=x_1+2x_{2}t$

$=x_1+4x_{2}t$

$y_1=x_1+3x_2+3x_1$

$y_2=x_1+4x_2+8x_1$

$y_1=2x_1+7x_2+12x_1$

i don't know how to find the adj$($A$),$ if you could go step by step i$\text{'}$d appreciate it$.$