T3 = T2 cos 40/cos30

in y component eq put the above eq in place of T3

T2sin40 - T2 cos 40/cos30 = T1

remember that T1 = 24 N (start of prob). Now the only unknown is T2 - solve

put the T2 in the x eq to get T3

QED

Note that the procedured here is exactly like the solution given you before.

Solve for separate one variable and substitute into the other equations. Repeat if necessary