ANSWER

EXPLANATION
The given equation is

We add the additive inverse of 31 which is -31 to both sides of the equation to get,

Simplify;


Answer:
ok so
Step-by-step explanation:
8x + 7 + 7x - 2=90=>
=> 15x+5= 90
=> 15x=90 - 5=>
=> 15x =85= x= 5.6666...
Answer:
Not completely sure if this is correct but I got
a: 12
b: 24sqrt2
h: 8sqrt2
Step-by-step explanation:
89+93+98 = 280
360 - 280 = 80 marks is needed for the last test