Answer the following seperate questions

19a.) 6x-1=4
19b.) 4w+3=10
Evaluate when t= -2
20a.) 5t-3
20b) the sequence 5+t, 5+2t, 5+3t, 5+4t..
20c.) 18- t²
20d) the sequence 2t- 3, 2t-5, 2t-7, 2t-9...
21.) Find the value of these expressions when p=2, q=3 and r=6
21a) 5q
21b) p+q
21c) qr
21d) 2p+ 3q
21e) r²