Please help me to solve these 4 problems step by step, thank you!

1. (5 pts) Solve the following system of equation by Gaussian elimination. Circle your pivots and be sure to label what your multiplier ;; is. 20+ 3y =1 6x + 5y = 15 2. (5 pts) Choose a value for b such that the system will have no solution. Find another b such that the system will have infinitely many solutions. 20+ 5y =3 dr+ 10y =10 3. (5 pts) Find the pivots and the solutions for the 4 x 4 system 2x+ y = 0 x + 2y + z = 0 y + 2z + t=0 z + 2t = 5 4. (5 pts) For which value of d will make this system singular (no third pivot)? 2x + 5y + z = 0 4x + dy + z = 2 y - z = 3