Question 12
Rohan keeps a total of $90$ guppies in $4$ fish tanks.
• There is $1$ more guppy in the $2$nd tank than in the $1$st tank.
• There are $2$ more guppies in the $3$rd tank than in the $2$nd tank.
• There are $3$ more guppies in the $4$th tank than in the $3$rd tank.
How many guppies are in the $4$th tank?
• There is $1$ more guppy in the $2$nd tank than in the $1$st tank.
• There are $2$ more guppies in the $3$rd tank than in the $2$nd tank.
• There are $3$ more guppies in the $4$th tank than in the $3$rd tank.
How many guppies are in the $4$th tank?