#include <stdio.h>

int main() {
	int mat[3][5];

	for (int i = 0; i<3; i++) {
		for (int j=0; j<5; j++) {
			mat[i][j] = i*10 + j;
		}
	}

	int (*a)[5];
	a = mat;
	//a = &mat[0]; //works as well

	for (int i=0; i<3; i++) {
		for (int j = 0; j<5; j++) {
			printf("%4d ", *(*(a+i) +j) );
		}
		printf("\n");
	}
}

arr[i][j] = (*(arr+i))[j] = *((*(arr+i))+j) = *(arr[i]+j)

#include <stdio.h>

int main() {
	int mat[3][5];

	for (int i = 0; i<3; i++) {
		for (int j=0; j<5; j++) {
			if (i==0 && j==0) {
				mat[i][j] = 111;
			}
			else {
				mat[i][j] = i*10 + j;
			}
		}
	}

	int (*a)[5];
	a = mat;
	//a = &mat[0]; //works as well


	for (int i=0; i<3; i++) {
		for (int j = 0; j<5; j++) {
			printf("%4d ", *( (*(a+i)) +j) );
		}
		printf("\n");
	}

	//Steps

	for (int i=0; i<3; i++) {
		printf("%p, %p\n", *(a++), mat[i]);
	}

	printf("Last element: %d\n", *((*(a-1)) + 4) );
}

Output

 111    1    2    3    4 
  10   11   12   13   14 
  20   21   22   23   24 
0x7fff8a9891b0, 0x7fff8a9891b0
0x7fff8a9891c4, 0x7fff8a9891c4
0x7fff8a9891d8, 0x7fff8a9891d8
Last element: 24