it’s an isoceles triangle so 180-64=116degrees = the sum of the other two equal angles in the triangle QRP and so angle QRP is 116÷2=58degrees, angles QRP and SRT are vertically opposite so they’re equal. The triangle SRT is also isosceles so 180-58= 122degrees = the sum of the last two equal base angles (including RST that you want to find) So lastly do 122÷2= 61degrees = angle RST
