hii guyz, i would REALLY like some help for these trig equation questions

thank you sooo much if you can helpp me !

if secx - tanx = 3/5, show that sinx = 8/17

if tanx = t, express sin2x and cos2x in terms of t. Find the values for t for which

(k+1)sin2x + (k-1)cos2x = k+1

thankyouuuu againn !!