equilibrium level of income from consumption , investment, govt expenditure demand for money

in this video we will learn how to Find Equilibrium level of output and interest rate
For an economy it is given :
C=200+0.8Yd
Yd=Y-tY
G=800
I=700-50i
t=0.25
L=0.25Y-62.5i
M/P=500
Find Equilibrium level of output and interest rate .
First we need to derive IS equation and LM Equation
then solve them to get equilibrium level of output and interest rate